An International Research Journal

Vol 25 No 3, 2016

AJP

SSN : 0971 - 3093

Vol 25, No 3, March 2016

25th Anniversary Year of AJP-2016


Asian Journal of Physics                                                                                                        Vol. 25 No 3 (2016) 221-232

 

Current trends in ground based solar magnetometry

 

 Sanjay Gosain

National Solar Observatory, 950 N Cherry Avenue, Tucson, AZ 85719, USA

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Continuous observations of the sun, over more than a century, have led to several important discoveries in solar astronomy. These include the discovery of the solar magnetism and its cyclic modulation, active region formation and decay and their role in energetic phenomena such as fares and coronal mass ejections (CMEs), fne structure and dynamics of the sunspots and small-scale organization of the magnetic fux in the form of fux tubes and so forth. In this article we give a brief overview of advancements in solar observational techniques in recent decades and the results obtained from the such observations. These include techniques to achieve high angular resolution, high spectral and polarimetric sensitivity and innovative new detectors. A wide range of spatial, temporal and spectral domains exploited by solar astronomers to understand the solar phenomena are discussed. Many new upcoming telescopes and instruments that are designed to address different aspects of solar physics problems are briefy described. Finally, we discuss the advantages of observing from the ground and how they can complement space-based observations. © Anita Publications. All rights reserved.

Current trends in ground based solar magnetometry.pdf
Sanjay Gosain

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Asian Journal of Physics                                                                                                        Vol. 25 No 3 (2016) 233-265


Watching the Sun from space

 

W. Dean Pesnell

NASA, Goddard Space Flight Center, Greenbelt, Maryland, USA

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Space-based solar observatories have made fundamental discoveries about the lifecycle of the solar magnetic field and how that field affects the solar system. Observing the Sun from space provides access to all wavelengths of light and eliminates the smearing of atmospheric seeing. Being in space means the emissions from the highly-ionized material that are the natural emissions of the corona can be measured. Continuous observations of the Sun can be made from a single satellite in certain orbits. This leads to unexpected discoveries, such as orbiting coronagraphs showing that sun grazing comets are the most common class of observed comets. Or when the coronal holes discovered with the solar X-ray telescopes on Skylab explained long-noticed correlations in particle fluxes from the Sun with solar longitudes. Space-based coronagraphs and heliospheric imagers are able to track coronal mass ejections from when they leave the Sun until they hit the Earth or another planet. In a more practical point, as humans have become more entwined in the use of technology, the magnetic field of the Sun has become more intrusive. Energetic particles and high-energy photons from solar fares can compromise humans and electronics in space. As a coronal mass ejection passes by and interacts with the Earth’s magnetosphere, it generates large currents at the Earth’s surface that can disrupt power distribution systems. The measurements of Sun made possible by being in space will be described, along with some highlights of the observatories that make them. © Anita Publications. All rights reserved.   

Keywords: Solar satellites; Solar telescopes; Solar activity, solar spectral irradiance

Watching the Sun from space.pdf
W Dean Pesnell

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Asian Journal of Physics                                                                                                      Vol. 25 No 3 (2016) 267-294


Solar activity and explosive transient eruptions


Ashok Ambastha

Udaipur Solar Observatory, Physical Research Laboratory, Udaipur, India

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We discuss active and explosive behavior of the Sun observable in a wide range of wavelengths (or energies) and spatio-temporal scales that are not possible for any other star. On the longer time scales, the most notable form of solar activity is the well known so called 11-year solar activity cycle. On the other hand, at shorter time scales of a few minutes to several hours, spectacular explosive transient events, such as, solar flares, prominence eruptions, and coronal mass ejections (CMEs) occur in the outer layers of solar atmosphere. These solar activity cycle and explosive phenomena influence and disturb the space between the Sun and planets. The state of the interplanetary medium, including planetary and terrestrial surroundings, or “the space weather”, and its forecasting has important practical consequences. The reliable forecasting of space weather lies in continuously observing of the Sun. We present an account of the recent developments in our understanding of these phenomena using both space-borne and ground-based solar observations.

Solar activity and explosive transient eruptions.pdf
Ashok Ambastha

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Asian Journal of Physics                                                                                                       Vol. 25 No 3 (2016) 295-310


Solar Ca II K Observations

 

Luca Bertello1, Alexei A. Pevtsov2, Andrey Tlatov3 and Jagdev Singh4
1National Solar Observatory, 3665 Discovery Drive, Boulder, CO 80303, USA
2National Solar Observatory, Sunspot, NM 88349, USA
3Kislovodsk Solar Station of Pulkovo Observatory, Kislovodsk, Russia
4Indian Institute of Astrophysics, Koramangala, Bangalore, India

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Some of the most important archives of past and current long-term solar synoptic observations in the resonance line of Ca II K are described here. These observations are very important for understanding the state of the solar magnetism on time scales up to several decades. The first observations of this kind began in 1904 at the Kodaikanal Observatory (India), followed by similar programs at different other locations. Regular full-disk Ca II K monitoring programs started in 1915 at the Mount Wilson Observatory (USA) and in 1917 at the National Solar Observatory of Japan. Beginning in 1919 and in 1926 regular observations were taken also at the Paris-Meudon Observatory (France) and at the ”Donati” solar tower telescope of the Arcetri Astrophysical Observatory in Italy, respectively. In 1926 the the Astronomical Observatory of the Coimbra University in Portugal started its own program of Ca II K observations. Although some of these programs have been terminated over the years, their data archives constitute a unique resource for studies of solar variability. In the early 1970s, the National Solar Observatory (NSO) at Sacramento Peak (USA) started a new program of daily Sun-as-a-star observations in the Ca II K line. Today the NSO is continuing these observations through its Synoptic Optical Long-term Investigations of the Sun (SOLIS) facility.

Solar Ca II K Observations.pdf
Luca Bertello, Alexei A Pevtsov, Andrey Tlatov and Jagdev Singh

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Asian Journal of Physics                                                                                                       Vol. 25 No 3 (2016)  311-324


Solar interior structure and dynamics


R Howe
University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom

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Helioseismology allows us to probe the interior structure and dynamics of the Sun, and long-term observa-tions allow us to follow their temporal variations. This review describes the important findings of recent years, covering the interior structure, the near-surface changes related to the solar cycle and possible deeper-seated variations, the interior rotation profile, and solar-cycle related changes in the zonal and meridional flows.

Solar interior structure and dynamics.pdf
R Howe

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Asian Journal of Physics                                                                                                        Vol. 25 No 3 (2016) 325-340


Solar subsurface flows from local helioseismology


Junwei Zhao1 and Ruizhu Chen2,1

1W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305-4085, USA

2Department of Physics, Stanford University, Stanford, CA 94305-4060, USA

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In this article, we review recent progresses in subsurface flows obtained from two local helioseismology methods: time-distance helioseismology and ring-diagram analysis. We review results in the following four topics: flows beneath sunspots and active regions, supergranular subsurface flows, shallow meridional flow and its variations with solar cycles, and meridional circulation in the deep solar interior. Despite recent advancements in methodology, modeling, and observations, many questions are still to be answered and a few topics remain controversial. More efforts, especially in numerical modeling and accurate interpretation of acoustic wave travel-time measurements, are needed to improve the derivations of subsurface flows.

Keywords: Sun: seismology; Sun:interior; Sun: subsurface lows

Solar subsurface flows from local helioseismology.pdf
Junwei Zhao and Ruizhu Chen

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Asian Journal of Physics                                                                                                       Vol. 25 No 3 (2016) 341-362


The solar cycle and solar dynamo models: past accomplishments, 

present status and a strategy for the 21st century


Mausumi Dikpati 

High Altitude Observatory, NCAR, 3280 Center Green Dr., Boulder, CO 80301, USA

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We describe the primary observational features of solar cycles, as seen in the photosphere, and review progress made over the past sixty years to simulate and predict these features using magneto-hydrodynamic dynamo models. The focus is on the so-called Babcock-Leighton flux-transport (BLFT) dynamo models, calibrated for the Sun, which so far have been the most successful in simulation, and the only ones tested for prediction. The proposed 21st century strategy for progress emphasizes the need (a) to use modern data assimilation techniques, so successful for Earth’s atmosphere simulation and prediction, to exploit all available solar observations, and (b) to generalize BLFT dynamo models to 3D to simulate and predict longitude-dependent cycle features. The 3D models must include (a) global HD and MHD instabilities in the solar tachocline, which probably create spatial patterns and time dependence that is reflected in surface observations, such as active longitudes, and (b) processes that capture the statistics and effects of emerging active regions that are tilted with respect to latitude circles, in order to accurately represent the surface source of poloidal fields, whose transport to the poles is responsible for polar field reversals.

The solar cycle and solar dynamo models: past accomplishments,present status and a strategy for the 21st century.pdf
Mausumi Dikpati

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Asian Journal of Physics                                                                                                        Vol. 25 No 3 (2016) 363-386


Solar origins of space weather

 

Kiran Jain and Rudolf W Komm

National Solar Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719, USA

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Space weather refers to the varying conditions in the space environment near Earth that are driven by the Sun and its changing magnetic field. The magnetic field originates in the interior of the Sun and extends throughout the solar atmosphere. We discuss the solar sources of space weather and focus on coronal mass ejections (CMEs), flares, and solar energetic particles (SEP) and on the on-going efforts to predict these eruptive events and their effect on space weather.

Solar origins of space weather.pdf
Kiran Jain and Rudolf W Komm

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Asian Journal of Physics                                                                                                        Vol. 25 No 3 (2016) 387-410


Predictions of solar cycle

 

Sushanta C. Tripathy

National Solar Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719, USA

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The Sun's activity measured through many of its proxies varies in a periodic manner with an average duration of about 11 years. The empirical relations based on the periodicity are considered as the first generation methods to predict the maximum amplitude of the next solar cycle.  These methods which are statistical in nature fall into two different categories: precursor methods and extrapolation methods and has been widely used in the later part of the 20th century. Recent advances include predictions based on non-linear methods and dynamo models, where the later predicts not only the maximum amplitude of the solar cycle but also the timing of the activity maximum.   In this review, we focus on different prediction methods and compare their outcome for previous cycles with an emphasis on cycle 24. We further analyze and compare various predictions for solar cycle 25 and beyond.

predictions of solar cycle.pdf
Sushanta C Tripathy

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Asian Journal of Physics                                                                                                        Vol. 25 No 3 (2016) 411-415


The solar-stellar connection


 Mark S Giampapa
National Solar Observatory, 950 N. Cherry Ave., Tucson, Arizona, USA

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A review of some principal results achieved in the area of stellar astrophysics with its origins in solar physics—the Solar-Stellar Connection—is presented from the perspective of an observational astronomer. The historical origins of the Solar-Stellar Connection are discussed followed by a review of key results from observations of stellar cycles analogous to the solar cycle in terms of parameters relevant to dynamo theory. A review of facets of angular momentum evolution and irradiance variations, each of which is determined by emergent, dynamo-generated magnetic ields,  is given. Recent considerations of the impacts of stellar magnetic activity on the ambient radiative and energetic particle environment of the habitable zone of exoplanet systems are summarized. Some anticipated directions of the Solar-Stellar Connection in the new era of astronomy as deined by the advent of transformative facilities are presented. © Anita Publications. All rights reserved.
Keywords: Dynamo; Magnetic activity; Cycles; Rotation; Solar- and late-type stars

The Solar-Stellar Connection.pdf
AJP_Mark S Giampapa

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Asian Journal of Physics                                                                                                       Vol. 25 No 3 (2016)  447-460


Solar physics research in the Russian subcontinent - current status and future


Alexei A. Pevtsov1, Yury A. Nagovitsyn2 , Andrey G. Tlatov3, Mikhail L. Demidov4

1National Solar Observatory, Sunspot, NM 88349, USA

2The Main (Pulkovo) Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe sh. 65,St. Petersburg, 196140 Russian Federation

3Kislovodsk Solar Station of Pulkovo Observatory, PO Box 145, Gagarina Str., 100, Kislovodsk, 357700 Russian Federation

4Institute of Solar-Terrestrial Physics SB RAS, 664033, Irkutsk, P.O. Box 291, Russian Federation

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Modern research in solar physics in Russia is a multifaceted endeavor, which includes multi-wavelength observations from the ground- and space-based instruments, extensive theoretical and numerical modeling studies, new instrument development, and cross-disciplinary and international research. The research is conducted at the research organizations under the auspices of the Russian Academy of Sciences and to a lesser extent, by the research groups at Universities. Here, we review the history of solar physics research in Russia, and provide an update on recent developments.

Keywords: Sun: history of research in Russia; Facilities: radio and optical observatories in Russia

Solar physics research in the Russian subcontinent - current status and future.pdf
AJP_Alexei A Pevtsov, Yury A Nagovitsyn, Andrey G Tlatov , and Mikhail L Demidov

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Asian Journal of Physics                                                                                                       Vol. 25 No 3 (2016)  461-498


A few perspectives of solar physics research in China - current status and future


Jingxiu Wang1, Mingde Ding2, Haisheng Ji3, Yuanyong Deng1, Yu Liu1,4, Zhong Liu1,4,

Zhongquan Qu1,4, Huaning Wang1, Lidong Xia5 and Yihua Yan1

1Key Lab of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China

2School of Astronomy and Space Science, Nanjing University, Nanjing, China

3Key Lab of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences,  Nanjing, China

4Yunnan Observatories, Chinese Academy of Sciences, Kunming, China

5School of Space Science and Physics, Shandong University, Weihai, China

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Solar physics research as an important discipline in astrophysics in China aims at improving the understanding of origin and variation of solar magnetic field and magnetic activity, and founding the basis for forecast of disastrous space weather. The current review is focused on the solar physics research in China in recent three years. Highlights in scientific research in solar magnetism, magnetic activity, coronal plasma, and space weather forecast are briefly summarized. Key advances in instrument development are reported in some necessary details. Future tendency and working direction are considered and discussed.

Keywords: Sun: activity; Sun-magnetic ields; solar wind; site testing; telescopes

A few perspectives of solar physics research in China - current status and future.pdf
AJP_Jingxiu Wang, Mingde Ding, Haisheng Ji, Yuanyong Deng, Yu Liu, Zhong Liu,Zhongquan Qu , Huaning Wang , Lidong Xia and Yihua Yan

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