Radio Signatures of Sunspot NOAA 12192

72nd International Astronautical Congress (IAC), Dubai, United Arab Emirates, 25-29 October 2021., 2021

This paper studies the correlation between the number of sunspots observed by the Sharjah Optical Observatory (SOO) and the solar radio bursts observed by the Sharjah Decametric Radio Telescope (SDRT) following the new 25 th solar cycle. Both observatories (SOO and SDRT) are located at the Sharjah Academy for Astronomy, Space Sciences, and Technology (SAASST) in the United Arab Emirates. As the Sun's magnetic field changes, the Sun's activity changes. The start of a solar cycle coincides with a solar minimum, referred to as the quiet radio Sun when the Sun has the least number of sunspots. Our SDRT observations reveal that the last quiet Sun phenomenon occurred between 2018 and 2019, i.e., the end of the 24 th solar cycle and the beginning of the new 25 th solar cycle. In 2020, solar activity and the number of sunspots saw a surge. The half period of the solar cycle is the solar maximum, or once the Sun has the highest number of sunspots. The 24 th solar cycle ended in December 2019 when the average number of sunspots achieved its minimum, and the first sunspots of the new cycle started to occur. Our preliminary results showed a strong correlation between the number of sunspots observed by the SOO and the detected radio bursts by the SDRT system. The two observatories' optical and radio contribute to the SAASST Space Weather program as part of the UAE Space Agency's vision to have a national program related to solar observations.

The Astrophysical Journal, 2016

We investigate the upper chromosphere and the transition region of the sunspot umbra using the radio brightness temperature at 34 GHz (corresponding to 8.8-mm observations) as observed by the Nobeyama Radioheliograph (NoRH). Radio free-free emission in the longer millimeter range is generated around the transition region, and its brightness temperature yields the region's temperature and density distribution. We use the NoRH data at 34 GHz by applying the Steer-CLEAN image synthesis. These data and the analysis method enable us to investigate the chromospheric structures in the longer millimeter range with high spatial resolution and sufficient visibilities. We also perform simultaneous observations of one sunspot using the NoRH and the Nobeyama 45-m telescope operating at 115 GHz. We determine that 115-GHz emission mainly originates from the lower chromosphere while 34-GHz emission mainly originates from the upper chromosphere and transition region. These observational results are consistent with the radio emission characteristics estimated from the current atmospheric models of the chromosphere. On the other hand, the observed brightness temperature of the umbral region is almost the same as that of the quiet region. This result is inconsistent with the current sunspot models, which predict a considerably higher brightness temperature of the sunspot umbra at 34 GHz. This inconsistency suggests that the temperature of the region at which the 34 GHz radio emission becomes optically thick should be lower than that predicted by the models.

2007

We present results from observations of narrowband solar millisecond radio spikes at 1420 MHz. Observing data were collected between February 2000 and December 2001 with the 15-m radio telescope at the Centre for Astronomy Nicolaus Copernicus University in Torun, Poland, equipped with a radio spectrograph that covered the 1352-1490 MHz frequency band. The radio spectrograph has 3 MHz frequency resolution and 80 microsecond time resolution. We analyzed the individual radio spike duration, bandwidth and rate of frequency drift. A part of the observed spikes showed well-outlined subtle structures. On dynamic radio spectrograms of the investigated events we notice complex structures formed by numerous individual spikes known as chains of spikes and distinctly different structure of columns. Positions of active regions connected with radio spikes emission were investigated. It turns out that most of them are located near the center of the solar disk, suggesting strong beaming of the spik...

2014

This paper aims to study the influence of sunspot number on High Frequency (HF) radio communications in Peninsular Malaysia for the years 2009 to 2011. Sunspots, which are a natural phenomenon that occurs due to magnetic activities on the Sun's surface, can be counted using smoothed sunspot number (SSN). HF signal propagates through the ionosphere where the ionospheric properties have been ionized by flares and prominences from sunspot number. This has significant effect on the stability of the ionosphere, resulting in the frequencies that can be used for HF communications to vary depending on the time of day, season, year and the 11-year solar cycle. This study was carried out during a period when the sunspot values rose from a low level in 2009 to a much higher level in 2011, making it suitable to observe the influence of sunspot number values on the HF frequencies employed. Maximum Usable Frequency (MUF) was determined based on HF transmission tests that were conducted from April 2009 to September 2011. It was observed that as the SSN values increase, the range of the operating HF frequencies and the numbers of frequencies that can be used also increase. This will, therefore, affect the median frequency that can be used for daily and monthly HF communications.

Advances in Space Research, 2003

At frequencies below 1 O-l 5 MHz, radio astronomical observations of the sun are routinely performed in space because'Earth's ionosphere effectively prohibits these low frequency emissions from reaching the ground. In terms of so&~ altitude, these frequencies correspond to about 2 Rs to 1 AU. At these low frequencies, a least four counterparts of the five classes of solar radio bursts typically observed by ground based telescopes can be detected, types I through IV, and type V bursts might possibly have been identified. All of these bursts observed from space vary considerably in occurrence rate between solar minimum and solar maximum. Some bursts, such as those associated with CMEs (types II and IV), are essentially not observed at all at solar minimum even though the CME rate only varies by about a factor of ten between maximum and minimum. The relatively common flare-associated radio bursts (type III) vary in occurrence rate rather substantially over the solar cycle, mimicking the variation in flare rate. However, the dominant emission in terms of occurrence rate or total energy at solar maximum is the interplanetary counterpart of type I storms, namely, type III storms. During the solar maximum years 2000-2001, more than 50% of all days in the year contain episodes of type III storms. Published by Elsevier Ltd on behalf of COSPAR.

Solar Physics, 2013

An unusual solar burst was observed simultaneously by two decameter radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) on 3 June 2011 in the frequency range 16-28 MHz. The observed radio burst has some unusual properties, which are not typical for the other types of solar radio bursts. The frequency drift rate of it was positive (about 500 kHz s -1 ) at frequencies higher than 22 MHz and negative (100 kHz s -1 ) at lower frequencies. The full duration of this event varies from 50 s up to 80 s, depending on the frequency. The maximum radio flux of the unusual burst reaches ≈ 10 3 s.f.u and its polarization does not exceed 10%. This burst has a fine frequencytime structure of unusual appearance. It consists of stripes with the frequency bandwidth 300-400 kHz. We consider that several accompanied radio and optical events observed by SOHO and STEREO spacecraft are possibly associated with the reported radio burst. A model that may interpret the observed unusual solar radio burst is proposed.

Symposium - International Astronomical Union, 2001

On 23 September 1998 there was a 3B/M7.1 flare event starting at 06:40 UT with more than 100 minute duration radio bursts of 1134 sfu peak flux at 2840 MHz and accompanying a CME. In this paper, the event is analyzed with the data observed by Beijing Astronomical Observatory (BAO), OSRA-Tremsdorf (AIP) and SSRT-ISTP. In particular, we compare the fine structures (FS) during the triggering phase revealed in different regimes and discuss their implications.

2006

We present complex radio bursts recorded by the radiospectrograph ARTEMIS-IV in the active period of January 2005. The wide spectral coverage of this recorder, in the 650-20 MHz range, permits an analysis of the radio bursts from the base of the Solar Corona to 2 Solar Radii; it thus facilitates the association of radio activity with other types of solar

In this paper we present an overview of solar radio observations at 11.2 GHz on Mets?hovi Radio Observatory (MRO). The data were observed during the solar cycles 23 and 24 (2001-2013) both in solar maxima and minimum. In total, 180 solar radio bursts, with varying intensities and properties, were observed. We compare our data series with other similar data sets. A good correlation can be found between the data series. It is concluded that one can conduct scientifically significant solar radio observations with a low cost instrument as the one presented in this paper.

Journal of Physics: Conference Series

The sun is an active star that produces large-scale energetic events, such as solar flares and coronal mass ejections (CMEs). These phenomena are observable across the electromagnetic spectrum, from gamma rays at hundreds of MeV to radio waves with wavelengths of tens of metres. Solar flares and CMEs can excite plasma oscillations which can emit radiation at metric and decametric wavelengths. These radio bursts are classified in five main types. This paper gives a solar radio burst type III (16 July 2017) in National Space Agency (ANGKASA), Banting, Selangor, Malaysia. Compact Astronomical Low-Cost Instrument for Spectroscopy in Transportable Observatories (CALLISTO) is used in this system to observe solar radio activities. The main applications for this CALLISTO is to observe a solar radio bursts and radio frequency interference (RFI) monitoring for astronomical science, education and outreach. The CALLISTO natively operates between 45MHz to 870MHz and its observed daily.