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Study of Cosmic-Ray Modulation during the Recent Unusual Minimum and Mini Maximum of Solar Cycle 24  

Aslam OPM   Submitted: 2015-07-29 19:22

After a prolonged and deep solar minimum at the end of Cycle 23, the current Solar Cycle 24 is one of the lowest cycles. These two periods of deep minimum and mini maximum are separated by a period of increasing solar activity. We study the cosmic-ray intensity variation in relation with the solar activity, heliospheric plasma and field parameters, including the heliospheric current sheet, during these three periods (phases) of different activity level and nature: (a) a deep minimum, (b) an increasing activity period and (c) a mini maximum. We use neutron monitor data from stations located around the globe to study the rigidity dependence on modulation during the two extremes, i.e., minimum and maximum. We also study the time lag between the cosmic-ray intensity and various solar and interplanetary parameters separately during the three activity phases. We also analyze the role of various parameters, including the current sheet tilt, in modulating the cosmic-ray intensity during the three different phases. Their relative importance and the implications of our results are also discussed.

Authors: O.P.M. Aslam & Badruddin
Projects: None

Publication Status: Accepted, Solar Physics
Last Modified: 2015-08-03 11:57
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Influence of cosmic-ray variability on the monsoon rainfall and temperature  

Aslam OPM   Submitted: 2014-11-23 10:29

We study the role of galactic cosmic ray (GCR) variability in influencing the rainfall variability in Indian Summer Monsoon Rainfall (ISMR) season. We find that on an average during "drought" (low ISMR) periods in India, GCR flux is decreasing, and during "flood" (high ISMR) periods, GCR flux is increasing. The results of our analysis suggest for a possibility that the decreasing GCR flux during the summer monsoon season in India may suppress the rainfall. On the other hand, increasing GCR flux may enhance the rainfall. We suspect that in addition to real environmental conditions, significant levitation/dispersion of low clouds and hence reduced possibility of collision/coalescence to form raindrops suppresses the rainfall during decreasing GCR flux in monsoon season. On the other hand, enhanced collision/coalescence efficiency during increasing GCR flux due to electrical effects may contribute to enhancing the rainfall. Based on the observations, we put forward the idea that, under suitable environmental conditions, changing GCR flux may influence precipitation by suppressing/enhancing it, depending upon the decreasing/increasing nature of GCR flux variability during monsoon season in India, at least. We further note that the rainfall variability is inversely related to the temperature variation during ISMR season. We suggest an explanation, although speculative, how a decreasing/increasing GCR flux can influence the rainfall and the temperature. We speculate that the proposed hypothesis, based on the Indian climate data can be extended to whole tropical and sub-tropical belt, and that it may contribute to global temperature in a significant way. If correct, our hypothesis has important implication for the sun - climate link.

Authors: Badruddin & Aslam, O.P. M.
Projects: None

Publication Status: Accepted to J. Atmos. Solar-Terr. Phys., DOI: http://dx.doi.org/10.1016/j.jastp.2014.11.005
Last Modified: 2014-11-24 07:26
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Study of the influence of solar variability on a regional (Indian) climate: 1901-2007  

Aslam OPM   Submitted: 2014-07-04 11:52

We use Indian temperature data of more than 100 years to study the influence of solar activity on climate. We study the Sun-climate relationship by averaging solar and climate data at various time scales; decadal, solar activity and solar magnetic cycles. We also consider the minimum and maximum values of sunspot number (SSN) during each solar cycle. This parameter SSN is correlated better with Indian temperature when these data are averaged over solar magnetic polarity epochs (SSN maximum to maximum). Our results indicate that the solar variability may still be contributing to ongoing climate change and suggest for more investigations.

Authors: Aslam, O.P. M., & Badruddin
Projects: None

Publication Status: Accepted to Adv. Space Research, DOI: 10.1016/j.asr.2014.06.019
Last Modified: 2014-07-04 11:52
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Fluctuations in the interplanetary electric potential and energy coupling between the solar-wind and the magnetosphere  

Aslam OPM   Submitted: 2013-12-09 22:50

We utilize solar rotation average geomagnetic index ap and various solar wind plasma and field parameters for four solar cycles 20-23. We perform analysis to search for a best possible coupling function at 27-day time resolution. Regression analysis using these data at different phases of solar activity (increasing including maximum/decreasing including minimum) led us to suggest that the time variation of interplanetary electric potential is a better coupling function for solar wind-magnetosphere coupling. We suspect that a faster rate of change in interplanetary electric potential at the magnetopause might enhance the reconnection rate and energy transfer from the solar wind into the magnetosphere. The possible mechanism that involves the interplanetary potential fluctuations in influencing the solar wind-magnetosphere coupling is being investigated.

Authors: Badruddin and Aslam, O.P.M.
Projects:

Publication Status: ASI Conference Series, 2013, Vol. 10, pp 103 ? 106
Last Modified: 2014-04-07 10:56
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Fluctuations in the interplanetary electric potential and energy coupling between the solar-wind and the magnetosphere  

Aslam OPM   Submitted: 2013-12-09 22:50

We utilize solar rotation average geomagnetic index ap and various solar wind plasma and field parameters for four solar cycles 20-23. We perform analysis to search for a best possible coupling function at 27-day time resolution. Regression analysis using these data at different phases of solar activity (increasing including maximum/decreasing including minimum) led us to suggest that the time variation of interplanetary electric potential is a better coupling function for solar wind-magnetosphere coupling. We suspect that a faster rate of change in interplanetary electric potential at the magnetopause might enhance the reconnection rate and energy transfer from the solar wind into the magnetosphere. The possible mechanism that involves the interplanetary potential fluctuations in influencing the solar wind-magnetosphere coupling is being investigated.

Authors: Badruddin and Aslam, O.P.M.
Projects: None

Publication Status: accepted to Proc. International Symposium on Solar-Terrestrial Physics 2012 (ISSTP 2012)
Last Modified: 2013-12-10 10:48
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Similarities and Distinctions in Cosmic-Ray Modulation during Different Phases of Solar and Magnetic Activity Cycles  

Aslam OPM   Submitted: 2013-12-09 22:47

We study the solar-activity and solar-polarity dependence of galactic cosmic-ray intensity (CRI) on the solar and heliospheric parameters playing a significant role in solar modulation. We utilize the data for cosmic-ray intensity as measured by neutron monitors, solar activity as measured by sunspot number (SSN), interplanetary plasma/field parameters, solar-wind velocity [V] and magnetic field [B], as well as the tilt of the heliospheric current sheet [{Lambda}] and analyse these data for Solar Cycles 20 - 24 (1965 - 2011). We divide individual Solar Cycles into four phases, i.e. low, high, increasing, and decreasing solar activity. We perform regression analysis to calculate and compare the CRI-response to changes in different solar/interplanetary parameters during (i) different phases of solar activity and (ii) similar activity phases but different polarity states. We find that the CRI-response is different during negative (A<0) as compared to positive (A>0) polarity states not only with SSN and {Lambda} but also with B and V. The relative CRI-response to changes in various parameters, in negative (A<0) as compared to positive (A>0) state, is solar-activity dependent; it is ~2 to 3 times higher in low solar activity, ~1.5 to 2 times higher in moderate (increasing/decreasing) activity, and it is nearly equal in high solar-activity conditions. Although our results can be ascribed to preferential entry of charged particles via the equatorial/polar regions of the heliosphere as predicted by drift models, these results also suggest that we should look for, any polarity-dependent response of solar wind and transport parameters in modulating CRI in the heliosphere.

Authors: Aslam, O.P.M., and Badruddin
Projects:

Publication Status: Solar Physics, 289, 2247-2268, 2014.
Last Modified: 2014-04-07 10:56
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Similarities and Distinctions in Cosmic-Ray Modulation during Different Phases of Solar and Magnetic Activity Cycles  

Aslam OPM   Submitted: 2013-12-09 22:47

We study the solar-activity and solar-polarity dependence of galactic cosmic-ray intensity (CRI) on the solar and heliospheric parameters playing a significant role in solar modulation. We utilize the data for cosmic-ray intensity as measured by neutron monitors, solar activity as measured by sunspot number (SSN), interplanetary plasma/field parameters, solar-wind velocity [V] and magnetic field [B], as well as the tilt of the heliospheric current sheet [{Lambda}] and analyse these data for Solar Cycles 20 - 24 (1965 - 2011). We divide individual Solar Cycles into four phases, i.e. low, high, increasing, and decreasing solar activity. We perform regression analysis to calculate and compare the CRI-response to changes in different solar/interplanetary parameters during (i) different phases of solar activity and (ii) similar activity phases but different polarity states. We find that the CRI-response is different during negative (A<0) as compared to positive (A>0) polarity states not only with SSN and {Lambda} but also with B and V. The relative CRI-response to changes in various parameters, in negative (A<0) as compared to positive (A>0) state, is solar-activity dependent; it is ~2 to 3 times higher in low solar activity, ~1.5 to 2 times higher in moderate (increasing/decreasing) activity, and it is nearly equal in high solar-activity conditions. Although our results can be ascribed to preferential entry of charged particles via the equatorial/polar regions of the heliosphere as predicted by drift models, these results also suggest that we should look for, any polarity-dependent response of solar wind and transport parameters in modulating CRI in the heliosphere.

Authors: Aslam, O.P.M., and Badruddin
Projects: None

Publication Status: accepted to Solar Physics
Last Modified: 2013-12-10 10:48
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Influence of solar and cosmic-ray variablity on climate  

Aslam OPM   Submitted: 2013-11-29 05:45

We analyze solar, geomagnetic and cosmic ray flux data along with rainfall and temperature data for almost five solar cycles. We provide evidence of significant influence of solar variability on climate. Specifically, we demonstrate association between lower (higher) rainfall and higher (lower) temperatures with increasing (decreasing) solar activity and decreasing (increasing) cosmic ray intensities. We propose a plausible scenario that accounts the results of our analysis.

Authors: Badruddin, O.P.M. Aslam and M. Singh
Projects: None

Publication Status: Proc. 31st Int. Cosmic Ray Conf. Lodz, SH 3.4, 1-3, 2009
Last Modified: 2013-12-02 10:46
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Study of the solar wind-magnetosphere coupling on different time scales  

Aslam OPM   Submitted: 2013-11-23 06:42

Solar wind-magnetosphere coupling, its causes and consequences have been studied for the last several decades. However, the assessment of continuously changing behaviour of the sun, plasma and field flows in the interplanetary space and their influence on geomagnetic activity is still a subject of intense research. Search for the best possible coupling function is also important for space weather prediction. We utilise four geomagnetic indices (ap, aa, AE and Dst) as parameters of geomagnetic activity level in the earth's magnetosphere. In addition to these indices, we utilise various solar wind plasma and field parameters for the corresponding periods. We analyse the geomagnetic activity and plasma/field parameters at yearly, half-yearly, 27-day, daily, 3-hourly, and hourly time resolutions. Regression analysis using geomagnetic and solar wind data of different time resolutions, over a continuous long period, and at different phases of solar activity (increasing including maximum/decreasing including minimum) led us to suggest that two parameters BV/1000(mV/m) and BV2(mV/s) are highly correlated with the all four geomagnetic activity indices not only at any particular time scale but at different time scales. It probably suggests for some role of the fluctuations/variations in interplanetary electric potential, its spacial variation [i.e., interplanetary electric field BV (mV/m)] and/or time variation [BV2 (mV/s)], in influencing the reconnection rate.

Authors: Badruddin and Aslam, O.P.M.
Projects: None

Publication Status: Published in Planetary and Space Science
Last Modified: 2013-11-25 08:32
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Solar Modulation of Cosmic Rays during the Declining and Minimum Phases of Solar Cycle 23: Comparison with Past Three Solar Cycles  

Aslam OPM   Submitted: 2013-11-23 06:36

We study solar modulation of galactic cosmic rays (GCRs) during the deep solar minimum, including the declining phase, of solar cycle 23 and compare the results of this unusual period with the results obtained during similar phases of the previous solar cycles 20, 21, and 22. These periods consist of two epochs each of negative and positive polarities of the heliospheric magnetic field from the north polar region of the Sun. In addition to cosmic-ray data, we utilize simultaneous solar and interplanetary plasma/field data including the tilt angle of the heliospheric current sheet. We study the relation between simultaneous variations in cosmic ray intensity and solar/interplanetary parameters during the declining and the minimum phases of cycle 23. We compare these relations with those obtained for the same phases in the three previous solar cycles. We observe certain peculiar features in cosmic ray modulation during the minimum of solar cycle 23 including the record high GCR intensity. We find, during this unusual minimum, that the correlation of GCR intensity is poor with sunspot number (correlation coefficient R=-0.41), better with interplanetary magnetic field (R=-0.66), still better with solar wind velocity (R=-0.80) and much better with the tilt angle of the heliospheric current sheet (R=-0.92). In our view, it is not the diffusion or the drift alone, but the solar wind convection that is the most likely additional effect responsible for the record high GCR intensity observed during the deep minimum of solar cycle 23.

Authors: Aslam, O.P.M., and Badruddin
Projects: None

Publication Status: Published in Solar Physics
Last Modified: 2013-11-25 08:32
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Abstracts by Author
Study of Cosmic-Ray Modulation during the Recent Unusual Minimum and Mini Maximum of Solar Cycle 24
Influence of cosmic-ray variability on the monsoon rainfall and temperature
Study of the influence of solar variability on a regional (Indian) climate: 1901-2007
Fluctuations in the interplanetary electric potential and energy coupling between the solar-wind and the magnetosphere
Fluctuations in the interplanetary electric potential and energy coupling between the solar-wind and the magnetosphere
Similarities and Distinctions in Cosmic-Ray Modulation during Different Phases of Solar and Magnetic Activity Cycles
Similarities and Distinctions in Cosmic-Ray Modulation during Different Phases of Solar and Magnetic Activity Cycles
Influence of solar and cosmic-ray variablity on climate
Study of the solar wind-magnetosphere coupling on different time scales
Solar Modulation of Cosmic Rays during the Declining and Minimum Phases of Solar Cycle 23: Comparison with Past Three Solar Cycles

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