The origin of the 10.7 cm flux

Tapping, K. F.; DeTracey, B.

doi:10.1007/bf00152171

Cited by 90 publications

(57 citation statements)

References 25 publications

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“…For freefree emissions, the spectrum decreases monotonically as the wavelength squared and thus is more intense at 10.7 than at 30 cm. Gyroresonant processes lead to a more complex spectrum, which on average peaks around 10 cm (Tapping & Detracey 1990). These processes have their counterpart in the UV part of the spectrum (White et al 2011).…”

Section: What Distinguishes F30 From F107?mentioning

confidence: 99%

The 30 cm radio flux as a solar proxy for thermosphere density modelling

Wit

Bruinsma²

2017

J. Space Weather Space Clim.

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The 10.7 cm radio flux (F10.7) is widely used as a proxy for solar UV forcing of the upper atmosphere. However, radio emissions at other centimetric wavelengths have been routinely monitored since the 1950 s, thereby offering prospects for building proxies that may be better tailored to space weather needs. Here we advocate the 30 cm flux (F30) as a proxy that is more sensitive than F10.7 to longer wavelengths in the UV and show that it improves the response of the thermospheric density to solar forcing, as modelled with DTM (Drag Temperature Model). In particular, the model bias drops on average by 0-20% when replacing F10.7 by F30; it is also more stable (the standard deviation of the bias is 15-40% smaller) and the density variation at the the solar rotation period is reproduced with a 35-50% smaller error. We compare F30 to other solar proxies and discuss its assets and limitations.

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Section: What Distinguishes F30 From F107?mentioning

confidence: 99%

The 30 cm radio flux as a solar proxy for thermosphere density modelling

Wit

Bruinsma²

2017

J. Space Weather Space Clim.

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“…The primarily coronal F 10.7 radio flux, the longest and most stable extant irradiance record, is monitored routinely by the Dominion Radio Astrophysical Observatory [Tapping and Detracey, 1990] and is available since 1947 from the National Geophysical Data Center. The Mg II index of chromospheric variability, available since 1978, is constructed from space-based measurements of the solar spectrum in the vicinity of the Mg II h and k Fraunhofer lines near 285 and 288 nm.…”

Section: Observed Irradiance Variationsmentioning

confidence: 99%

Solar extreme ultraviolet irradiance: Present, past, and future

et al. 2011

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[1] New models of solar extreme ultraviolet (EUV) irradiance variability are constructed in 1 nm bins from 0 to 120 nm using multiple regression of the Mg II and F 10.7 solar activity indices with irradiance observations made during the descending phase of cycle 23. The models have been used to reconstruct EUV spectra daily since 1950, annually since 1610, to forecast daily EUV irradiance and to estimate future levels in cycle 24. A two-component model developed by scaling the observed rotational modulation of the two solar indices underestimates the solar cycle changes that the Solar EUV Experiment (SEE) reports at wavelengths shorter than 40 nm and longer than 80 nm. A three-component model implemented by including an additional term derived from the smoothed Mg II index better reproduces the measurements at all wavelengths. The three-component model is consistent with variations in the EUV energy from 0 to 45 nm that produces the far ultraviolet (FUV) terrestrial dayglow observed by the Global Ultraviolet Imager (GUVI). However, the spectral structure of this third component is complex, and its origin is uncertain. Analogous two-and three-component models are also developed with absolute scales determined by the NRLEUV2 spectrum of the quiet Sun rather than by the SEE average spectrum. Assessment of the EUV absolute spectrum and variability of the four different models indicate that during solar cycle 23, the EUV irradiance (0 to 120 nm) increased 100 ± 30%, from 2.9 ± 0.2 to 5.8 ± 0.9 mWm −2 , and may have been as low as 1.9 ± 0.5 mWm −2 during the 17th-century Maunder Minimum. Near the peak of upcoming solar cycle 24, EUV irradiance is expected to increase 40% to 80% above the 2008 minimum values.

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“…The origin of 2800 MHz radiation is the thermal emission of plasma trapped in magnetic loops of the active region and is consequently related to the photospheric magnetic field flux of active regions. The 10.7 cm emission is mainly due to free-free radiation, as mentioned by Tapping & DeTracey (1990). The 10.7 cm rotation rate concerns the global activity component of the solar corona.…”

Section: Datamentioning

confidence: 97%

Solar activity cycle and rotation of the corona

Mouradian

Bocchia

Botton

2002

A&A

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Abstract. In this paper we consider the dependence of the coronal rotation period on solar activity. We analyzed the 10.7 cm radio emission flux covering cycles 19 to 22. We have established a new method for studying the rotation rate: by identifying the flux pulses with the recurrence of active longitudes. We first determined the frequency domain of the rotation and then analyzed each cycle separately. The entire domain of 51.7 years was divided into 480-day sections, which were analyzed independently and then grouped into frames for each cycle in order to study the time variation of prominent frequencies (Fig. 4). Power spectra were obtained with the Maximum Entropy Method. The 10.7 cm emission rotation varies accordingly to the activity level, i.e. at the activity maxima the synodic period of rotation is about 25.4 days and at the minima it is around 30 days; it is 32 days for the quiet Sun (Table 1). Empirical relations give the ratio of maximum and minimum sidereal rotation rate with respect to sunspot number (Fig. 6). During the cycle increase phase, the average acceleration of the rotation period is 0.8• /d per year, in decreasing phase that average is only −0.5.

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The origin of the 10.7 cm flux

Cited by 90 publications

References 25 publications

The 30 cm radio flux as a solar proxy for thermosphere density modelling

The 30 cm radio flux as a solar proxy for thermosphere density modelling

Solar extreme ultraviolet irradiance: Present, past, and future

Solar activity cycle and rotation of the corona

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