Inner Radiation Belt Simulations of the Proton Flux Response in the South Atlantic Anomaly during the Geomagnetic Storm of 15 May 2005

A test particle simulation code was developed to simulate the inner proton belt response during the intense geomagnetic storm of May 15, 2005. The guiding center model was implemented in order to compute the proton trajectories with energy range 70-180 MeV. The time-varying magnetic field model implemented in the simulations was computed by the Tsyganenko model TS05 with the associated inductive electric field. One of the most important features of the Low-Earth Orbit (LEO) environment is the presence of the South Atlantic Anomaly, which imposes a dangerous radiation load on most of the LEO missions. The objective of this research is to investigate the proton flux variations in the anomaly region with respect to space weather conditions. The results showed that during the main phase of the geomagnetic storm, the proton flux in the SAA was decreased, whereas throughout the initial and recovery phases, the proton flux was increased at most of the altitudes. Numerical results were confirmed by satellite measurements.

Investigation on the characteristics of the South Atlantic Anomaly

The South Atlantic Anomaly (SAA) is known for its weak Earth’s magnetic field strength. In this research, power spectrum analysis method was applied on the Horizontal intensity of the Earth’s magnetic field with data sample rate used at 1 min. Four active periods on 18 March 2012, 10 March 2012, 25 April 2012, and 30 June 2013 which represent the occurrence of geomagnetic storms and 4 normal periods on 25 March 2012, 21 March 2012, 4 April 2012, and 15 June 2013 which indicate no geomagnetic storm event were examined. Research was conducted by analyzing the SAA region where comparisons were made between the middle latitude region and the high latitude region. The results indicate that the SAA region tends to be persistent, and this may be due to the ring current. The middle latitude region experienced a mixture of persistent and antipersistent characteristics and this may be due to the transportation of plasma and seasonal weather variations. The high latitude region tends to be antipersistent. This may indicate that the high latitude region is influenced by geomagnetic storms and the aurora.

Trapped Proton Fluxes Estimation Inside the South Atlantic Anomaly Using the NASA AE9/AP9/SPM Radiation Models along the China Seismo-Electromagnetic Satellite Orbit

The radiation belts in the Earth’s magnetosphere pose a hazard to satellite systems and spacecraft missions (both manned and unmanned), heavily affecting payload design and resources, thus resulting in an impact on the overall mission performance and final costs. The NASA AE9/AP9/SPM radiation models for energetic electrons, protons, and plasma provide useful information on the near-Earth environment, but they are still incomplete as to some features and, for some energy ranges, their predictions are not based on a statistically sufficient sample of direct measurements. Therefore, it is of the upmost importance to provide new data and direct measurements to improve their output. In this work, the AP9 model is applied to the China Seismo-Electromagnetic Satellite (CSES-01) orbit to estimate the flux of energetic protons over the South Atlantic Anomaly during a short testing period of one day, 1 January 2021. Moreover, a preliminary comparison with proton data obtained from the High-Energy Particle Detector (HEPD) on board CSES-01 is carried out. This estimation will serve as the starting ground for a forthcoming complete data analysis, enabling extensive testing and validation of current theoretical and empirical models.

A Statistical Analysis of Plasma Bubbles Observed by Swarm Constellation during Different Types of Geomagnetic Storms

Based on the observations of Ionospheric Bubble Index (IBI) data from the Swarm mission, the characteristics of plasma bubbles are investigated during different types of geomagnetic storms recorded from 2014 to 2020. The geometrical constellation of the Swarm mission enabled us to investigate the altitudinal profile of the IBIs during different activity levels in a statistical mean. Results show that the majority of IBIs associated with moderate storms are observed at low altitudes and the probability of observing IBIs at high altitudes (Swarm-B) increases with the increase in storm level. This is confirmed by observing the F2 layer peak height (hmF2) during super storm events at larger altitudes using COSMIC data. The maximum number of IBIs is recorded within the South Atlantic Anomaly (SAA) region with a long duration time and tends to increase only during dusk time. Both the large duration time and number of IBIs over the South Atlantic Anomaly (SAA) suggest that the gradient in the electron density and the depression in the magnetic field are the main factors controlling IBI events. Also, the IBIs at high altitudes are larger at sunset and at low altitudes pre-midnight. In addition, the occurrence of IBIs is always larger in the northern hemisphere than in the southern hemisphere irrespective of the type of storm, as well as during the summer months. Moreover, there is no correlation between the duration time of IBIs and both the altitudinal observation of the IBIs and the storm type. Seasonal occurrence of IBIs is larger during equinoxes and vice versa during solstices irrespective of both the type of storm and the altitude of the satellite. The large number of IBIs during equinoxes agrees with the previous studies, which expect that the large electron density is a developer of steeper . Large occurrences of super storm IBIs observed within the pre-midnight during summer and at sunset during equinoxes are a novel observation that needs further investigation. Also, the majority of IBIs are observed a few hours after geomagnetic substorms, which reflects the role of the Disturbance Dynamo Electric Field (DDEF) as a main driver of IBIs.

CubeSat Observation of the Radiation Field of the South Atlantic Anomaly

The movement of the South Atlantic Anomaly has been observed since the end of the last century by many spacecrafts equipped with various types of radiation detectors. All satellites that have observed the drift of the South Atlantic Anomaly have been exclusively large missions with heavy payload equipment. With the recent rapid progression of CubeSats, it can be expected that the routine monitoring of the South Atlantic Anomaly will be taken over by CubeSats in the future. We present one-and-a-half years of observations of the South Atlantic Anomaly radiation field measured by a CubeSat in polar orbit with an elevation of 540 km. The position is calculated by an improved centroid method that takes into account the area of the grid. The dataset consists of eight campaigns measured at different times, each with a length of 22 orbits (~2000 min). The radiation data were combined with GPS position data. We detected westward movement at 0.33°/year and southward movement at 0.25°/year. The position of the fluence maximum featured higher scatter than the centroid position.