scholarly journals ANALISIS VARIASI FREKUENSI KRITIS DAN KETINGGIAN LAPISAN IONOSFER DI ATAS KUPANG

2018 ◽  
Vol 2 (2) ◽  
pp. 85-91
Author(s):  
Husni Husni ◽  
Ali Warsito ◽  
Asnawi Husin
Keyword(s):  
Solar Activity ◽  
High Frequency ◽  
Critical Frequency ◽  
Radio Communication ◽  
Radio Communications ◽  
Reflected Waves ◽  
The Hours ◽  
Critical Frequency Fof2 ◽  
High Frequency Waves ◽  
Sun Activity

ABSTRAK Variasi perubahan frekuensi kritis lapisan F2 (foF2) dan ketinggian lapisan F2 (h'F2) di atas Kupang selama tahun 2014 mengalami perubahan yang bervariasi dimana hal ini bergantung pada aktivitas matahari, semakin tinggi tingkat aktivitas matahari semakin tinggi pula tingkat variasi pada foF2 dan h'F2, sebaliknya semakin rendah tingkat aktivitas matahari semakin berkurang pula tingkat variasi foF2 dan h'F2 variasi perubahan terhadap lapisan F diindikasikan dengan penurunan dan peningkatan nilai foF2 dan h'F2. Peningkatan nilai foF2 rata-rata terjadi pada pukul  07.00 WITA mencapai maksimumnya pada pukul 12.00-14.00 WITA siang hari dan dikuti dengan penurunan nilai foF2 pada malam hari yang mencapai minimumnya pada pukul 05.00-06.00 WITA pagi. Selama tahun 2014, ketinggian lapisan F2 memiliki tiga pola peningkatan yang berbeda, (1) peningkatan ketinggian pada jam tengah hari seperti yang terjadi pada bulan Januari – April, (2) peningkatan pada jam tengah malam hingga menjelang matahari terbit, jam-jam tengah hari dan  sore hingga malam hari terjadi pada bulan Mei – Agustus (3) peningkatan pada pada jam tengah malam hingga menjelang matahari terbit dan jam-jam tengah hari seperti pada bulan September – Desember. Dalam pemanfaatannya sebagai media pantul gelombang komunikasi radio frekuensi tinggi (HF), karakteristik ionosfer di atas Kupang selama tahun 2014, memiliki kemampuan memantulkan gelombang frekuensi tinggi berada pada rentang 2-19.2 MHz dengan ketinggian yang berada pada rentang 179 – 550 Km. Akan mengakibatkan gagalnya komunikasi radio frekuensi tinggi, apabila menggunakan frekuensi lebih besar atau lebih kecil dari frekuensi yang dapat bekerja tersebut. Kata Kunci : Aktivitas matahari, Frekuensi kritis F2, ketinggian lapisan F2, komunikasi radio, frekuensi tinggi. ABSTRACT The ionospheric critical frequency (foF2) and the F2 layer height (h'F2) variation over Kupang during 2014 period unchanged varied where it is dependent on solar activity, the higher the level of solar activity the higher the level of variation in foF2 and h'F2, conversely the lower level of sun activity diminishing the level of variation foF2 and h'F2 variation changes to the F layer is indicated by a decrease and an increase in the value of foF2 and h'F2. Increasing the value of the average foF2 occurred at 07:00 pm reaching it's maximum at noon and 12:00 to 14:00 pm followed by impairment foF2 at night, which reached it's minimum at morning 5:00 to 6:00 pm. During 2014, the altitude of the F2 has three patterns different upgrade, (1) an increase in height on the hour midday as happened in January-April, (2) an increase in the hours of midnight until before sunrise, hours noon and afternoon until the evening occurred in May-August (3) an increase in the hours of midnight until near sunrise and midday hours as in September-December. In the media utilization as reflected waves of high frequency radio communications (HF), characteristics of the ionosphere above Kupang during 2014, has the ability to reflect high frequency waves that are in the range of 2 - 19.2 MHz with a height that is in the range 179-550 Km. Will lead to high frequency radio communication failure, when using a frequency of greater or smaller than the frequency that can work. Keywords: solar activity, the critical frequency of F2, F2 layer heights, radio communications, high frequency.

The Impact of Sunspots Number on Critical Frequencies foF2 for the IONOSPHERIC Layer-F2 Over Erbil Station During the Down Phase of Solar Cycle 24

2021 ◽  
Vol 19 (8) ◽  
pp. 157-168
Author(s):  
Wafaa H.A. Zaki
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Sunspot Number ◽  
Critical Frequency ◽  
Radio Communication ◽  
Ionospheric Layer ◽  
Solar Cycle 24 ◽  
Critical Frequency Fof2 ◽  
Cycle 24 ◽  
The Impact

The ionosphere layer (F2) is known as the most important layer for High frequency (Hf) radio communication because it is a permanent layer and excited during the day and night so it is able to reflect the frequencies at night and day due to its high critical frequency, and this layer is affected by daily and monthly solar activity. In this study the characteristics and behavior of F2 layer during Solar cycle 24 were studied, the effect of Sunspots number (Ri) on the critical frequency (foF2), were investigated for the years (2015, 2016, 2017, 2018, 2019, 2020) which represents the down phase of the solar cycle 24 over Erbil station (36° N, 44° E) by finding the critical frequency (foF2) values, the layer’ s impression times are determined for the days of solstice as well as equinox, where the solar activity was examined for the days of the winter and summer solstice and the days of the spring and autumn equinoxes for a period of 24 hours by applied the International Reference Ionosphere model IRI (2016). The output data for foF2 were verified by using the IRI-Ne- Quick option by specifying the time, date and Sunspot number parameters. Statistical analysis was caried out through the application of the Minitab (version 2018) in order to find the correlation between the critical frequency (foF2) of Ionospheric layer F2 and Sunspot number. It was concluded that the correlation is strong and positive, this indicate that critical frequency (foF2) increase with increasing Sunspots number (Ri) for solar cycle 24.

scholarly journals On the relation between ionospheric parameters and sunspot number

2020 ◽  
Vol 1 ◽  
Author(s):  
Chris Hall ◽  
Magnar Gullikstad Johnsen
Keyword(s):  
Solar Activity ◽  
Change Point ◽  
Critical Frequency ◽  
Auroral Oval ◽  
Change Points ◽  
Observation Site ◽  
F Region ◽  
Critical Frequency Fof2 ◽  
E Region ◽  
The Relationship

AbstractIn a recent study, mid-latitude ionospheric parameters were compared with solar activity; it was suggested that the relationship between these, earlier assumed stable, might be changing with time (Lastovicka, 2019). Here, the information is extended to higher latitude (69.6°N, 19.2E) and further back in time. For the ionospheric F-region (viz. the critical frequency, FoF2) the same behaviour is seen with a change-point around 1996. For the ionospheric E-region (viz. the critical frequency, foE), change-points are less obvious than in the mid-latitude study, presumably owing to the observation site lying under the auroral oval.

scholarly journals Weak ionization of the global ionosphere in solar cycle 24

2014 ◽  
Vol 32 (7) ◽  
pp. 809-816 ◽  
Author(s):  
Y. Q. Hao ◽  
H. Shi ◽  
Z. Xiao ◽  
D. H. Zhang
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Critical Frequency ◽  
Extreme Ultraviolet ◽  
Maximum Level ◽  
Electron Content ◽  
Total Electron ◽  
Weakly Ionized ◽  
Critical Frequency Fof2 ◽  
Cycle 24

Abstract. Following prolonged and extremely quiet solar activity from 2008 to 2009, the 24th solar cycle started slowly. It has been almost 5 years since then. The measurement of ionospheric critical frequency (foF2) shows the fact that solar activity has been significantly lower in the first half of cycle 24, compared to the average levels of cycles 19 to 23; the data of global average total electron content (TEC) confirm that the global ionosphere around the cycle 24 peak is much more weakly ionized, in contrast to cycle 23. The weak ionization has been more notable since the year 2012, when both the ionosphere and solar activity were expected to be approaching their maximum level. The undersupply of solar extreme ultraviolet (EUV) irradiance somewhat continues after the 2008–2009 minimum, and is considered to be the main cause of the weak ionization. It further implies that the thermosphere and ionosphere in the first solar cycle of this millennium would probably differ from what we have learned from the previous cycles of the space age.

scholarly journals Solar Cycle variations of ƒ<i>o</i>F2 from IGY to 1990

2002 ◽  
Vol 20 (10) ◽  
pp. 1677-1685 ◽  
Author(s):  
N. K. Sethi ◽  
M. K. Goel ◽  
K. K. Mahajan
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Data Center ◽  
Critical Frequency ◽  
Equatorial Ionosphere ◽  
Digital Form ◽  
Low Latitudes ◽  
The World ◽  
Critical Frequency Fof2 ◽  
Modelling And Forecasting

Abstract. Noontime monthly median values of F2-layer critical frequency foF2 (m) for some ionospheric stations representing low- and mid-latitudes are examined for their dependence on solar activity for the years 1957 (IGY) to 1990. This is the period for which ionospheric data in digital form is available in two CD-ROMs at the World Data Center, Boulder. It is observed that at mid-latitudes, foF2 (m) shows nearly a linear relationship with R12 (the 12-month running average of the Zurich sunspot number), though this relation is nonlinear for low-latitudes. These results indicate some departures from the existing information often used in theoretical and applied areas of space research.Key words. Ionosphere (equatorial ionosphere; mid-latitude ionosphere; modelling and forecasting)

First VIKING results: high frequency waves

1988 ◽  
Vol 37 (3) ◽  
pp. 469-474 ◽  
Author(s):  
A Bahnsen ◽  
M Jespersen ◽  
E Ungstrup ◽  
R Pottelette ◽  
M Malingre ◽  
...  
Keyword(s):  
High Frequency ◽  
High Frequency Waves

Preferential acceleration of heavy ions from thermal velocities

1968 ◽  
Vol 46 (10) ◽  
pp. S638-S641 ◽  
Author(s):  
D. B. Melrose
Keyword(s):  
Frequency Spectrum ◽  
High Frequency ◽  
Heavy Ions ◽  
Crab Nebula ◽  
Low Frequency ◽  
High Frequency Waves ◽  
Hydromagnetic Waves ◽  
The Crab Nebula ◽  
Low Frequency Waves

The acceleration of ions from thermal velocities is analyzed to determine conditions under which heavy ions can be preferentially accelerated. Two accelerating mechanisms involving high-and low-frequency hydromagnetic waves respectively are considered. Preferential acceleration of heavy ions occurs for high-frequency waves if the frequency spectrum falls off faster than (frequency)−1. For the low-frequency waves heavy ions are less effectively accelerated than lighter ions. However, very heavy ions can be preferentially accelerated, the abundances of the very heavy ions being enhanced by a factor Ai over the thermal abundances. Acceleration of ions in the envelope of the Crab nebula is considered as an example.

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