GALACTIC COSMIC RAY VARIABILITY IN THE HIGH AND MID LATITUDES DURING SOLAR CYCLES 22 AND 23

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TABLE OF CONTENT

Title Page                    —————————————————————     i

Certification                —————————————————————     ii

Approval page             —————————————————————     iii

Dedication                  —————————————————————     iv

Acknowledgement      —————————————————————     v

List of Tables              —————————————————————     vi

List of Figures             —————————————————————     vii

Table of Content ———————————————————————      viii

Abstract                      —————————————————————     x

CHAPTER ONE: INTRODUCTION

1.1         Cosmic rays     ————————————————————-      1

1.2          Types of cosmic rays       ————————————————     1

1.2.1      Galactic Cosmic ———————————————————-                  4

1.2.2        Solar Cosmic Rays (SCRs)    ——————————————-   5

1.2.3        Anomalous Cosmic Rays (ACRs) ————————————– 5

1:3          Variability of galactic cosmic rays ————————————-    6

1.4          Cosmic ray modulation   ————————————————-    7

1.4.2      Geomagnetic field modulation   —————————————–   9

1.4.3       Solar modulation    ——————————————————-     9

   1:5       Current missions to understand cosmic ray sources and transport —–         11

   1.5.1     Equations (S) For Cosmic Ray Transport ——————————- 11

  1.  Solar activity and the cycles 22 and 23    —————————–    13

1.8        Purpose of study   ——————————————————          14

CHAPTER TWO: LITERATURE REVIEW

2.1        Recent review literature on day – to – day variability   ————— 15

2.2        Review literature on cosmic ray variability —————————-    16

2.3        Factors affecting cosmic ray production and/or transport ———–19

2.4        Solar cycle 22 and 23   —————————————————-     21

CHAPTER THREE: SOURCES OF DATA

3.1       Cosmic ray data———————————————————–                   23

3.2       Data on solar wind parameters ——————————————   23

CHAPTER FOUR: METHODS OF DATA ANALYSIS

4.1         Calculation of yearly average —————————————– 24

4.2         Calculation of percentage variation of yearly average data —–25

4.3         Method of analysis for yearly average data ————————-25 

CHAPTER FIVE:  RESULTS AND DISCUSSION

5.1           Result ———————————————————————–    32

 CHAPTER SIX:  CONCLUSION

6.1           Conclusions ————————————————————–      35

APPENDICES

Appendix i   Yearly average for quietest conditions ——————-          36

Appendix ii   Yearly average for all conditions ——————————-           37

Appendix iii   Yearly average for all minus quietest conditions ———-38

Appendix iv   Yearly average for disturbed conditions —————-          39

Appendix v     % Variation of yearly average for quietest conditions ——40

Appendix vi    % variation of yearly average for all conditions ———- 41

Appendix vii    % Variation of yearly average for all minus quietest conditions–     42

Appendix viii   % Variation of yearly average for disturbed conditions –43

References

ABSTRACT

Galactic cosmic rays are modulated in the hliosphere primarily due to the global merged interaction regions with intense magnetic field which leads to a decrease in the galactic cosmic rays throughout the heliosphere.  Using long term averages of solar wind (SW) component parameters in addition to cosmic ray count rates of two high latitude Neutron monitor stations (Apatity and Thule) and two mid latitude stations (Newark and Tbilisi) with different rigidity cut-offs, we analyzed the effect of these SW components on the counts rates under different interplanetary magnetic field (IMF) disturbance levels. From first order partial correlation, we found that the total interplanetary magnetic field (Total B) was the most dominant modulating parameter especially during quiet conditions and the solar wind dynamic pressure (SWDP) was more effective during disturbed conditions. The influence of the more subtle parameters like solar wind speed (SWS), Z component of IMF (Bz) and solar wind density were masked by these dominant parameters vis IMF (Total B) and SWDP. Also, cosmic ray count rates on these stations studied showed similar annual variation trend, with station of lowest cut-off rigidity having highest amplitude and vice versa, confirming cut-off rigidity as another important modulating factor.

CHAPTER ONE

1.1       COSMIC RAYS

The cosmic rays (CRs) are energetic charged subatomic particles originating from the outer space with lifetime of the order 106 years or longer, incident at the top of the terrestrial atmosphere and produce showers of particles on interaction with the atmosphere which penetrate and impact the earth’s atmosphere and sometimes  reach the earth’s surface. Apartfrom particles associated with solar flare, cosmic Rays come from outside the solar system. The incoming charged particles are modulated by the solar wind, the expanding magnetized plasma generated by the sun, which decelerate and partially excludes the lower energy cosmic rays from the inner solar system. CRs are mostly pieces of atoms: protons, electrons, and atomic nuclei which have had all of the surrounding electrons stripped during their high-speed (almost the speed of light) passage through the space.

The need to study cosmic rays and their interaction with earth is driven by the understanding that CRs are the major source of ion production in the lower atmosphere (troposphere and stratosphere), therefore, the electrical properties of the atmosphere such as atmospheric electric current, lightening production and thunder cloud formation e.t.c., can be affected by cosmic rays (Ermakov and Komozokov, 1992). It also damages micro-electronics and life outside the protection of the atmosphere and Geomagnetic field. CRs have sufficient energy to alter the state of element in electronic integrated circuit, causing transient errors to occur, such as corrupted data in electronic memory devices or incorrect performance of central processing unit (CPU). It ionizes the nitrogen and oxygen molecules in the atmosphere which leads to a number of chemical reaction; and is responsible for the continuous production of a number of unstable isotopes in the atmosphere of the earth, such as carbon 14 (14C).

Cosmic Rays are one of the most important barriers standing against interplanetary travel and pose threat to electronics placed aboard outgoing probe.  Magnetic shielding for spacecraft have to be considered in order to minimize damages to electronics and human by cosmic rays ( Nancy, 2005).

1.2                               Types of Cosmic Rays

Types of cosmic rays are classified according to two categories; one, depending on their sources, they are of three types, galactic cosmic rays (GCRs), solar cosmic rays (SCRs), and anomalous cosmic rays(ACR).Two, depending on interaction with space, they are of two types, primary and secondary cosmic rays. Cosmic rays originate as primary cosmic rays, which are those originally produced in various astrophysical processes. Primary cosmic rays are composed primarily of 98% nuclei and 2% electrons. Of the nuclei, 87% are protons, 12% helium nuclei, and 1% heavier nuclei (Andreas, 2008). Heavier nuclei examples, carbon, oxygen, iron and other nuclei synthesized in stars are primary cosmic rays.

Secondary cosmic rays are caused by decay of primary cosmic rays as they impact on atmospheric materials; they include neutron, pion, and muon.Nuclei such as lithium, beryllium and boron (which are not abundant end-product of stellar nucleosynthesis) are secondaries. Antiprotons and positrons are also in large part secondary cosmic Rays.One primary “ray” can cause 50 secondary “rays”, a cascading effect that eventually gets down the ground. The shower of secondaries can spread over a large area. We are constantly being bombarded by these particles.