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Search results for , issue "Vol 17, No 1 (2019)" : 5 Documents clear

ASTIGMATISMA TELESKOP 50 CM F/3,8 UNTUK OBSERVATORIUM NASIONAL TIMAU Rhorom Priyatikanto
Jurnal Sains Dirgantara Vol 17, No 1 (2019)
Publisher : Lembaga Penerbangan dan Antariksa Nasional

Observatorium Nasional Timau akan menjadi fasilitas observatorium di bagian tenggara Indonesia, dilengkapi dengan teleskop optik kelas sub-meter dan meter. Sebuah teleskop tipe Ritchey-Chretien dengan bukaan 50 cm dan panjang fokus 150 cm diharapkan menjadi kuda kerja dari program survei. Dalam makalah ini, tingkatan astigmatisma dari teleskop dievaluasi dengan menggunakan pendekatan geometris. Hasilnya menunjukkan bahwa astigmatisma cukup kecil dan tidak signifikan dalam mempengaruhi kinerja sistem keseluruhan. Besarnya direpresentasikan oleh koefisien Zernike Z22 yang nilainya 200 nm, jauh lebih kecil dari panjang gelombang operasional dan ukuran pixel kamera.

ANALYSIS OF WEST NUSA TENGGARA RAINFALL TO ENSO PHENOMENON BASED ON TRMM 3B43 DATA Amalia Nurlatifah
Jurnal Sains Dirgantara Vol 17, No 1 (2019)
Publisher : Lembaga Penerbangan dan Antariksa Nasional

West Nusa Tenggara is part of the Indonesian Maritime Continent region whose weather conditions are heavily influenced by the dynamics of the Pacific Ocean and Indian Ocean. One of the dynamics that influenced the rainfall condition was the ENSO phenomenon (El Nino and La Nina). This study analyzes rainfall response in West Nusa Tenggara to ENSO phenomenon. The research data was taken from TRMM 3B43 with a monthly temporal resolution and 0.25o spatial resolution. Based on the analysis, it was found that El Nino phenomenon characterized by the heating of Sea Surface Temperature (SST) in Nino 3.4 had an impact on decreasing rainfall in NTB. In contrast, the La Nina phenomenon characterized by the cooling of SST in Nino 3.4 tends to have an impact on increasing rainfall in NTB. Nevertheless, the value of the increase and decrease of Nino 3.4 SST anomaly and rainfall in NTB itself is not linear. This is probably due to the magnitude of the ENSO phenomenon only regulating rainfall changes only, not regulating how far, how strong, or how much rainfall is reduced or increased due to the influence of the ENSO phenomenon. This is evidenced by the small correlation coefficient between Nino 3.4 SST anomaly and rainfall in NTB where the strongest value only reached -0.4 in the JJA season. In the JJA season, the correlation coefficient of Nino 3.4 SST Anomaly and rainfall in NTB tend to be negative and strongest when compared to other seasons. This is probably due to the spatial coherence of NTB rainfall in the JJA season better than the other season. Spatially, almost all areas in NTB in El Nino month experience a decrease in rainfall. In contrast, almost all areas in NTB in the month of La Nina experience an increase in rainfall. The smallest decrease or increase in rainfall during El Nino or La Nina takes place in the southwestern of Sumbawa Island. That means, the influence of the ENSO phenomenon in this region tends to be weak.

PROBABILITAS LONTARAN MASSA KORONA BERDASARKAN PARAMETER MEDAN MAGNET UNIVARIAT Rhorom Priyatikanto; Emanuel Sungging Mumpuni; Tiar Dani; Farahhati Mumtahana; Nana Suryana
Jurnal Sains Dirgantara Vol 17, No 1 (2019)
Publisher : Lembaga Penerbangan dan Antariksa Nasional

Forecasting of flare occurrence and coronal mass ejection (CME) are necessary since those energetic phenomena are able to effectively influence the space weather on Earth. In this study, we analyzed four magnetic parameters of active region: (1) mean gradient of horizontal magnetic field (meangbh), (2) mean helicity (meanjzh), (3) mean photospheric magnetic free energy (meanpot) and (4) mean gradient of total field (meangbt) and their potential usage for the input in CME prediction based on linear statistics. Obtained that among those four parameters, meangbt is the best parameter for the purpose mentioned. Active regions with meanbgt ≤ 96 Gauss/Mm probably produce flare with CME and the True Skill Score from this prediction is ~20%. Eventhough this achieved score is considerably low, it is proportionally comparable with respect to the other work. Prediksi flare dan lontaran massa korona (coronal mass ejection, CME) perlu dilakukan mengingat kedua peristiwa energetik tersebut dapat mempengaruhi cuaca antariksa di Bumi secara efektif. Pada studi kali ini, kami menganalisis empat parameter magnetik daerah aktif: (1) rerata gradien medan horisontal (meangbh), (2) rerata arus puntir (meanjzh), (3) rerata gradien medan magnet total (meangbt), dan (4) rerata energi magnetik bebas fotosfer (meanpot) serta potensinya untuk sebagai input dalam prediksi CME berbasis statistik linier. Hasilnya, diantara keempat parameter tersebut, meangbt merupakan parameter terbaik untuk keperluan tersebut. Daerah aktif dengan meangbt ≤ 96 Gauss/Mm berpotensi menghasilkan flare yang disertai CME dan True Skill Score dari prediksi ini adalah ~20%. Meski masih tergolong rendah, skor yang didapatkan dapat disandingkan secara proporsional dengan pekerja oleh peneliti lain.

ANALISIS ARUS LISTRIK DAN MEDAN MAGNET PADA DAERAH AKTIF PENGHASIL FLARE AR NOAA 12017 Johan Muhamad
Jurnal Sains Dirgantara Vol 17, No 1 (2019)
Publisher : Lembaga Penerbangan dan Antariksa Nasional

Flare Matahari terjadi akibat adanya pelepasan energi magnetik di suatu daerah aktif. Energi tersebut dihasilkan akibat adanya arus listrik yang mengalir di struktur korona daerah aktif. Pada daerah aktif penghasil flare, sistem arus listrik dan medan magnetnya terbentuk sedemikian rupa sehingga energi magnetiknya terakumulasi di daerah tertentu. Oleh karena itu, pemahaman akan karakteristik sistem kelistrikan dan kemagnetan daerah aktif penghasil flare sangat penting dikuasai agar prakiraan flare dapat dilakukan. Dengan menggunakan data medan magnet fotosfer dari Spaceweather HMI AR Patch (SHARP), kami melakukan analisis terhadap daerah aktif NOAA 12017 (AR 12017) yang menghasilkan banyak flare, termasuk flare kelas M dan X pada bulan Maret 2014. Kami menunjukkan bagaimana cara menurunkan parameter-parameter kelistrikan dan kemagnetan pada daerah aktif ini sepanjang periode flare tanggal 27-29 Maret 2014. Kami menemukan bahwa arus listrik vertikal pada daerah aktif ini menjadi semakin tidak netral menjelang terjadinya flare. Kami juga menemukan bahwa flare-flare terjadi pada awalnya di daerah dengan akumulasi energi yang tinggi, yakni di daerah dengan medan magnet yang tergeser dengan kuat akibat kemunculan fluks baru. Hasil ini menunjukkan bahwa daerah aktif AR 12017 dapat diidentifikasi sebagai penghasil flare, bahkan sebelum flare terjadi berdasarkan karaketeristik sistem arus dan konfigurasi medan magnetnya.

RELATIONSHIP AND PERIODICITY OF SOLAR CORONAL HOLE AREA WITH THE SOLAR WIND SPEED AND GEOMAGNETIC ACTIVITY Tiar Dani, M.Si
Jurnal Sains Dirgantara Vol 17, No 1 (2019)
Publisher : Lembaga Penerbangan dan Antariksa Nasional

Space weather disturbances during solar minimum are more dominantly caused by the appearance of the coronal hole in the sun. In this paper, we developed tools called DeLuNa to detect and calculate the geo-effective corona hole area based on 19.3nm images from the Atmospheric Imaging Assembly instrument on Solar Dynamics Observatory (SDO/AIA193). The results from geoeffective coronal hole detection and measurement from 2016 - 2018 then used to conduct cross-correlation (cc) analysis and wavelet analysis with the solar wind speed and Dst index. We found that an increase in the area of the coronal hole will cause solar wind speed to increase at 3.17 days later (cc = 0.65). Increasing the area of the coronal hole will also cause Dst index to decrease at 3.58 days later (cc = -0.35). While the decrease in the Dst index will only take 2 hours since the increased of the solar wind speed (cc = -0.59). Wavelet analysis short-term periodicities, i.e. 27, 13.5 and 7-9 days. The observed periodicities show that changes in solar wind speed and geomagnetic storm during minimum solar activity are more dominant caused by the geoeffective coronal hole total area.

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