Sains Malaysiana 52(8)(2023): 2309-2322

http://doi.org/10.17576/jsm-2023-5208-11

Examining Solar Flare Effects on Earth's Ionosphere using Ground-Based Measurements

(Pengkajian Kesan Nyalaan Suria terhadap Ionosfera Bumi menggunakan Pengukuran Dasar)

NURUL SHAZANA ABDUL HAMID^1,2,*, RAJA ADIBAH RAJA HALIM¹, IDAHWATI SARUDIN³, AKIMASA YOSHIKAWA^4,5 & AKIKO FUJIMOTO⁶

¹Department of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

²Space Science Centre (ANGKASA), Institute of Climate Change, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor, Malaysia

³School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia

⁴Department of Earth and Planetary Sciences, Faculty of Sciences, 33 Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan

⁵International Research Center for Space and Planetary Environmental Science (i-SPES), Kyushu University, 819-0395 Fukuoka, Japan

⁶Department of Artificial Intelligence, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, 680-4, Kawazu, Iizuka, Fukuoka 820-8502, Japan

Received: 28 January 2023/Accepted: 2 August 2023

Abstract

This study investigated the simultaneous effects of solar flares (SFs) on both the D and E layers of Earth's ionosphere. The analysis focused on the M and X-class SFs that occurred during the 24th solar cycle as these two classes of SFs are known to produce significant effects on Earth’s environment, particularly during the daytime period. The data utilized to detect the SF events in this study were ground-based magnetometer data from the equatorial regions. Effects of the selected SF events on the E layer were investigated based on the EUEL index constructed using the geomagnetic data. Meanwhile, the changes in the strength of radio VLF signals in the D ionospheric layer during the selected SF events were monitored using Sudden Ionospheric Disturbance (SID) data. Two case studies were performed which consisted of four SF events from a total of 23 events that were detected by geomagnetic data during the period of study. Further analysis on the selected SF events showed the common effects of SFs on the D layer, which is the increment on the VLF signal measured from the SID stations although a different response was detected in the EUEL index variations. This indicates that the VLF signal always shows an increment even though a decrement in the ionization of the E layer occurs as a result of the SF events. The difference in responses could be attributed to the distinct changes in electron density of both layers during the SF occurrence. Further studies are needed to elucidate the underlying mechanism responsible for this unique response, utilizing appropriate parameters such as total electron content, as well as the electron density data to thoroughly analyze the ionospheric response during SF events.

Keywords: EEJ current; geomagnetic field; SID; solar flare; VLF signal

Abstrak

Penyelidikan ini mengkaji kesan nyalaan suria (SF) secara serentak pada kedua-dua lapisan D dan E ionosfera Bumi. Analisis memfokuskan kepada SF kelas M dan X yang berlaku semasa kitaran suria ke-24 kerana kedua-dua kelas SF ini menghasilkan kesan yang ketara ke atas persekitaran Bumi, terutamanya pada waktu siang. Data yang digunakan untuk mengesan kejadian SF dalam kajian ini ialah data magnetometer cerapan dasar dari rantau-rantau khatulistiwa. Kesan kejadian SF yang dipilih pada lapisan E telah dikaji berdasarkan indeks EUEL yang dibina menggunakan data medan geomagnet tersebut. Sementara itu, data Gangguan Ionosfera Mendadak (SID) digunakan untuk memantau perubahan kekuatan isyarat radio VLF pada lapisan D ionosfera untuk kejadian SF yang terpilih. Dua kajian kes telah dilakukan yang terdiri daripada empat kejadian SF daripada 23 peristiwa yang dikesan oleh data geomagnet sepanjang tempoh kajian. Analisis lanjut mengenai kejadian SF terpilih telah memerhatikan kesan umum SF pada lapisan D iaitu kenaikan pada isyarat VLF yang diukur dari stesen SID walaupun tindak balas berbeza dikesan dalam variasi indeks EUEL. Ini menunjukkan bahawa isyarat VLF sentiasa menunjukkan kenaikan walaupun pengurangan dalam pengionan lapisan E terjadi kesan daripada kejadian SF. Perbezaan dalam tindak balas ini boleh disebabkan oleh perubahan yang berbeza dalam ketumpatan elektron pada kedua-dua lapisan semasa berlakunya kejadian SF. Kajian lanjut diperlukan untuk menerangkan mekanisme tindak balas unik ini dengan menggunakan parameter yang sesuai seperti jumlah kandungan elektron serta data ketumpatan elektron untuk menganalisis secara menyeluruh akan tindak balas ionosfera semasa kejadian SF.

Kata kunci: Arus EEJ; isyarat VLF; medan geomagnet; nyalaan suria; SID

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*Corresponding author; email: shazana.ukm@gmail.com