• Journal of The Korean Astronomical Society
• /
• v.56 no.1
• /
• pp.117-124
• /
• 2023

A Forbush decrease (FD) is a depression of cosmic ray (CR) intensity observed by ground-based neutron monitors (NMs). The CR intensity is thought to be modulated by the heliospheric magnetic structures including the interplanetary coronal mass ejection (ICME) surrounding the Earth. The different magnitude of the decreasing in intensity at each NM was explained only by the geomagnetic cutoff rigidity of the NM station. However, sometimes NMs of almost the same cutoff rigidity in northern and southern hemispheres observe the asymmetric intensity depression magnitudes of FD events. Thus, in this study we intend to see the effects on CR intensity modulation of FD event recorded at different NMs due to different ICME propagation directions as an additional parameter in the model explaining the CR modulation. Fortunately, since 2006 the coronagraphs of twin spacecraft of the STEREO mission allow us to infer the propagation direction of ICME associated with the FD event in 3-dimension with respect to the Earth. We suggest the hypothesis that the asymmetric CR modulations of FD events are determined by the propagation directions of the associated ICMEs.

• Journal of Aerospace System Engineering
• /
• v.18 no.4
• /
• pp.89-95
• /
• 2024

This paper introduces an effective and convenient method for utilizing onboard memory space to process remote commands, telemetry, and interplanetary network protocol data in satellite onboard systems. By enhancing the doubly linked list data structure to store and make accessible variable-length communication protocol data either sequentially or at variable locations, the paper enhances memory capacity utilization. The concept of 'grape' is introduced into the doubly linked list data structure to manage variable-length data and its access, with performance verification conducted through its reference implementation. This novel approach to linked lists is termed 'grape.'

• Journal of Astronomy and Space Sciences
• /
• v.21 no.2
• /
• pp.153-166
• /
• 2004

Interplanetary trajectories using the gravity assists are studied for future Korean interplanetary missions. Verifications of the developed softwares and results were performed by comparing data from ESA's Mars Express mission and previous results. Among the Jupiter exploration mission scenarios, multi-planet gravity assist mission to Jupiter (Earth-Mars-Earth-Jupiter Gravity Assist, EMEJGA trajectory) requires minimum launch energy ($C_3$) of 29.231 $Km^2$/$S^2$ with 4.6 years flight times. Others, such as direct mission and single-planet(Mars) gravity assist mission, requires launch energy ($C_3$) of 75.656 $Km^2$/$S^2$ with 2.98 years flight times and 63.590 $Km^2$/$S^2$ with 2.33 years flight times, respectively. These results show that the planetary gravity assists can reduce launch energy, while EMEJGA trajectory requires the longer flight time than the other missions.

• The Bulletin of The Korean Astronomical Society
• /
• v.33 no.1
• /
• pp.37.1-37.1
• /
• 2008

• Journal of Astronomy and Space Sciences
• /
• v.24 no.2
• /
• pp.119-124
• /
• 2007

The relation between substorm occurrences and HILDCAA events has been an issue. We have studied the association of particle injections with substorm onsets during HILDCAA intervals for the first half of year 2003. The examination of aurora images observed by IMAGE spacecraft and electron flux data measured by LANL satellites exhibits a close association of repetitive particle injections with substorm activity. We also find that HILDCAA events can occur equally frequently during slow speed solar wind streams as long as the interplanetary magnetic field exhibits Alfvenic wave feature.

• Bulletin of the Korean Space Science Society
• /
• 2004.04a
• /
• pp.41-41
• /
• 2004

We report the results on the investigation of the association of solar wind dynamics and the occurrence of geosynchronous relativistic electron events. This study analyzed E>2MeV electron fluxes measured by GOES 10 satellite and solar wind parameters by ACE satellite for April, 1999 to December, 2002. Most of the relativistic events during the time period are found to be accompanied by the prolonged period of quiet solar wind dynamics which is characterized as low solar wind pressure, weak interplanetary magnetic field, and fast fluctuations in IMF Bz. (omitted)

• The Bulletin of The Korean Astronomical Society
• /
• v.32 no.1
• /
• pp.86.1-86.1
• /
• 2007

• Journal of The Korean Astronomical Society
• /
• v.34 no.4
• /
• pp.317-319
• /
• 2001

The response of the earth's magnetosphere to the variation of the solar wind parameters and Interplanetary magnetic field (IMF) has been stud}ed by using a high-resolution, three-dimension magnetohydrodynamic (MHD) simulation when the WIND data of velocity Vx, plasma density, dynamic pressure, By and Bz every 1 minute were used as input. Large electrojet and magnetic storm which occurred on October 21 and 22 are reproduced in the simulation (fig. 1). We have studied the energy transfer and tail reconnect ion in association with geomagnetic storms.

• Bulletin of the Korean Space Science Society
• /
• 2007.10a
• /
• pp.37-37
• /
• 2007

• The Bulletin of The Korean Astronomical Society
• /
• v.33 no.2
• /
• pp.35.1-35.1
• /
• 2008