L-shell and energy dependence of magnetic mirror point of charged particles trapped in Earth’s magnetosphere
Abstract In the Earth’s inner magnetosphere, there exist regions like plasmasphere, ring current, and radiation belts, where the population of charged particles trapped along the magnetic field lines is more. These particles keep performing gyration, bounce and drift motions until they enter the los...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2020-09-01
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| Series: | Earth, Planets and Space |
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| Online Access: | http://link.springer.com/article/10.1186/s40623-020-01264-5 |
| _version_ | 1818308880759783424 |
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| author | Pankaj K. Soni Bharati Kakad Amar Kakad |
| author_facet | Pankaj K. Soni Bharati Kakad Amar Kakad |
| author_sort | Pankaj K. Soni |
| collection | DOAJ |
| description | Abstract In the Earth’s inner magnetosphere, there exist regions like plasmasphere, ring current, and radiation belts, where the population of charged particles trapped along the magnetic field lines is more. These particles keep performing gyration, bounce and drift motions until they enter the loss cone and get precipitated to the neutral atmosphere. Theoretically, the mirror point latitude of a particle performing bounce motion is decided only by its equatorial pitch angle. This theoretical manifestation is based on the conservation of the first adiabatic invariant, which assumes that the magnetic field varies slowly relative to the gyro-period and gyro-radius. However, the effects of gyro-motion cannot be neglected when gyro-period and gyro-radius are large. In such a scenario, the theoretically estimated mirror point latitudes of electrons are likely to be in agreement with the actual trajectories due to their small gyro-radius. Nevertheless, for protons and other heavier charged particles like oxygen, the gyro-radius is relatively large, and the actual latitude of the mirror point may not be the same as estimated from the theory. In this context, we have carried out test particle simulations and found that the L-shell, energy, and gyro-phase of the particles do affect their mirror points. Our simulations demonstrate that the existing theoretical expression sometimes overestimates or underestimates the magnetic mirror point latitude depending on the value of L-shell, energy and gyro-phase due to underlying guiding centre approximation. For heavier particles like proton and oxygen, the location of the mirror point obtained from the simulation deviates considerably (∼ 10°–16°) from their theoretical values when energy and L-shell of the particle are higher. Furthermore, the simulations show that the particles with lower equatorial pitch angles have their mirror points inside the high or mid-latitude ionosphere. |
| first_indexed | 2024-12-13T07:21:18Z |
| format | Article |
| id | doaj.art-7927b1562027424992962bba47a511fb |
| institution | Directory Open Access Journal |
| issn | 1880-5981 |
| language | English |
| last_indexed | 2024-12-13T07:21:18Z |
| publishDate | 2020-09-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Earth, Planets and Space |
| spelling | doaj.art-7927b1562027424992962bba47a511fb2022-12-21T23:55:25ZengSpringerOpenEarth, Planets and Space1880-59812020-09-0172111510.1186/s40623-020-01264-5L-shell and energy dependence of magnetic mirror point of charged particles trapped in Earth’s magnetospherePankaj K. Soni0Bharati Kakad1Amar Kakad2Indian Institute of GeomagnetismIndian Institute of GeomagnetismIndian Institute of GeomagnetismAbstract In the Earth’s inner magnetosphere, there exist regions like plasmasphere, ring current, and radiation belts, where the population of charged particles trapped along the magnetic field lines is more. These particles keep performing gyration, bounce and drift motions until they enter the loss cone and get precipitated to the neutral atmosphere. Theoretically, the mirror point latitude of a particle performing bounce motion is decided only by its equatorial pitch angle. This theoretical manifestation is based on the conservation of the first adiabatic invariant, which assumes that the magnetic field varies slowly relative to the gyro-period and gyro-radius. However, the effects of gyro-motion cannot be neglected when gyro-period and gyro-radius are large. In such a scenario, the theoretically estimated mirror point latitudes of electrons are likely to be in agreement with the actual trajectories due to their small gyro-radius. Nevertheless, for protons and other heavier charged particles like oxygen, the gyro-radius is relatively large, and the actual latitude of the mirror point may not be the same as estimated from the theory. In this context, we have carried out test particle simulations and found that the L-shell, energy, and gyro-phase of the particles do affect their mirror points. Our simulations demonstrate that the existing theoretical expression sometimes overestimates or underestimates the magnetic mirror point latitude depending on the value of L-shell, energy and gyro-phase due to underlying guiding centre approximation. For heavier particles like proton and oxygen, the location of the mirror point obtained from the simulation deviates considerably (∼ 10°–16°) from their theoretical values when energy and L-shell of the particle are higher. Furthermore, the simulations show that the particles with lower equatorial pitch angles have their mirror points inside the high or mid-latitude ionosphere.http://link.springer.com/article/10.1186/s40623-020-01264-5Earth’s inner magnetosphereTrapped particle trajectoriesMagnetic mirror pointsTest particle simulation |
| spellingShingle | Pankaj K. Soni Bharati Kakad Amar Kakad L-shell and energy dependence of magnetic mirror point of charged particles trapped in Earth’s magnetosphere Earth, Planets and Space Earth’s inner magnetosphere Trapped particle trajectories Magnetic mirror points Test particle simulation |
| title | L-shell and energy dependence of magnetic mirror point of charged particles trapped in Earth’s magnetosphere |
| title_full | L-shell and energy dependence of magnetic mirror point of charged particles trapped in Earth’s magnetosphere |
| title_fullStr | L-shell and energy dependence of magnetic mirror point of charged particles trapped in Earth’s magnetosphere |
| title_full_unstemmed | L-shell and energy dependence of magnetic mirror point of charged particles trapped in Earth’s magnetosphere |
| title_short | L-shell and energy dependence of magnetic mirror point of charged particles trapped in Earth’s magnetosphere |
| title_sort | l shell and energy dependence of magnetic mirror point of charged particles trapped in earth s magnetosphere |
| topic | Earth’s inner magnetosphere Trapped particle trajectories Magnetic mirror points Test particle simulation |
| url | http://link.springer.com/article/10.1186/s40623-020-01264-5 |
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