An International Research Journal

AJP Vol 16 No 2&3, 2007

AJP

SSN : 0971 - 3093

Vol  16, No. 2 & 3, April-September, 2007

Special Issue on Space Weather, Vol 16, Nos 2&3, 2007

 

Preamble

The magnetic field in the space around the Sun called heliosphere evolves in response to the magnetic field at the base of the photosphere of the Sun. This evolution, together with the rotation of the Sun, drives space weather through the continually changing conditions of the solar wind and the magnetic field  embedded within it. Given this broad framework, it is apparent that the near-earth environment, viz. the earth’s magnetosphere and ionosphere are continually affected by the Sun. Hence conditions in the near-earth environment are linked to the underlying disturbances in the solar magnetic field and can manifest themselves in different ways depending on the local conditions on the Sun. The phenomenal growth in the space-based technological systems, in the recent times, coupled with the growing needs of modern civilization makes it imperative for mankind to be able to predict “weather” or in other words, the conditions prevailing in the near-earth environment and the inner heliosphere i.e. the space between the Sun and the Earth. Thus, this entire space environment  is governed indirectly and/or directly by processes taking place in the Sun itself.

The Sun affects space not only by its radiation but also by spewing out particulate matter (or plasma) containing energetic electrons and protons. A vast variety of energetic solar phenomena like solar flares, filament eruptions, coronal mass ejections and other solar wind phenomena constantly change the space environment generating a variety of plasma instabilities under the influence of solar and interplanetary magnetic and electric fields. As a result of these violent activities going on in the Sun, the interplanetary medium is not homogeneous but interspersed with density irregularities that affect the radio wave propagation by producing scintillations akin to the twinkling of stars in the visible radiation. Solar wind interaction with the Earth’s magnetosphere can cause changes in the earth’s ionosphere that can adversely affect radio communications. Energetic solar particles are also immensely hazardous to the well-being of the artificial satellites that are ever increasing in numbers. The Earth’s ionosphere too displays a variety of plasma instabilities that cause irregularities in its density structure.

Space weather studies are basically meant to unfold this coupled and highly complex Sun-Earth system or Sun-Planet system. The importance of understanding space weather is so overwhelming that a large number of solar and ionospheric scientists are coming together all over the world in a connected effort to address the ultimate goal of predicting solar and space weather phenomena. Coordinated multi-wavelength observations and theoretical modeling are going on hand-in-hand to understand how to cope up with “living with a star” i.e. the Sun and the interest in this field is growing by leaps and bounds.

This special volume is a humble attempt to address and review a few  issues on space weather. It contains articles on basic physical processes in the Sun which lead to energetic and often explosive activity as well as the effects of these on the interplanetary medium and the ionosphere of the Earth. The authors of the articles are all eminent scientists actively working in the field. The articles attempt to bring out how near or how far we are in our understanding of the Sun, the solar wind and space weather. All the articles have been given editorial attention so far as general readability is concerned; the technical issues are left mostly to the authors valuable judgement. We express our sincere gratitude to all the authors for their cooperation and enthusiasm in contributing to this special volume. We thank Ms Karanjgaokar for help with the manuscripts and figures.

 

P Janardhan, Hari Om Vats, K N Iyer and B G Anandarao

Guest Editors


Asian Journal of Physics

Vol 16, Nos 2&3 (2007) 97-307

 

CONTENTS

Guest Editorial

Space weather simulations in 3D MHD from the Sun to Earth and beyond to 100 AU: A modeler’s perspective of the present State of  the Art
Murray Dryer
                                                                                                                                                                                                                                    97

 

The magnetic origin of coronal mass ejections

A Nindos                                                                                                                                                                                                                                          123
 

Magnetic field of the coronal mass ejection source regions                                                           

Debi Prasad Choudhary                                                                                                                                                                                                                  147

 

Solar flare reconnection, plasmoid ejection, loop-top X-ray sources and associated radio bursts

M Karlický                                                                                                                                                                                                                                       165


Solar radio bursts and space weather

Stephen M White                                                                                                                                                                                                                              189

 

Insights from ground and space based observations of long lasting low density anomalies at 1 AU 

P Janardhan, S Ananthakrishnan, and V Balasubramanian                                                                                                                                                           209

 

Electron acceleration in solar noise storms                                                                    

Prasad Subramanian                                                                                                                                                                                                                       233

 

Impact of space weather events on the coupling of ionosphere and thermosphere over low latitudes 
R Sekar and D Chakrabarti
                                                                                                                                                                                                            247

 

Effects of recent space weather events in the equatorial and low latitude F-region in the Brazilian sector: A review

Y Sahai, F Becker-Guedes, P R Fagundes, F L Guarnieri, A J de Abreu, R de Jesus, V G Pillat, W L C Lima and J A Bittencourt                                            273


Rotation of the Sun and its atmosphere

Hari Om Vats                                                                                                                                                                                                                                   291

 

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