Creating space plasma from the ground

Abstract

We have performed an experiment to compare as directly as realizable the ionization production rate by HF radio wave energy versus by solar EUV. We take advantage of the commonality that ionization production by both ground‐based high‐power HF radio waves and by solar EUV is driven by primary and secondary suprathermal electrons near and above ~20 eV. Incoherent scatter radar (ISR) plasma‐line amplitudes are used as a measure of suprathermal electron fluxes for ISR wavelengths near those for 430 MHz and are indeed a clean measure of such for those fluxes sufficiently weak to have negligible self‐damping. We present data from an HF heating experiment on November 2015 at Arecibo, which even more directly confirm the only prior midlatitude estimate, of order 10% efficiency for conversion of HF energy to ionospheric ionization. We note the theoretical maximum possible is ~1/3, while ~1% or less reduces the question to near practical irrelevance. Our measurements explicitly confirm the prediction that radio‐frequency production of artificial ionospheres can be practicable, even at midlatitudes. Furthermore, that this midlatitude efficiency is comparable to efficiencies measured at high latitudes (which include enhancements unique to high latitudes including magnetic zenith effect, gyrofrequency multiples, and double resonances) requires reexamination of current theoretical thinking about soft‐electron acceleration processes in weakly magnetized plasmas. The implications are that electron acceleration by any of a variety of processes may be a fundamental underpinning to energy redistribution in space plasmas.

Distinctive Features of Langmuir and Ion‐Acoustic Turbulences Induced by O‐ and X‐Mode HF Pumping at EISCAT

“…A generation of very intense radio-induced optical emission in red and green lines with a high ratio of green to red line of 0.35-0.5 in the course of the X-mode pump pulses was found by Blagoveshchenskaya et al (2014). Carlson and Mantas (1982) and Carlson et al (2016) have found that the flux of accelerated electrons can produce an increased production of ionization. The EISCAT UHF radar observations clearly demonstrated that electron density enhancements by 50-70% from the background level were observed above the reflection height of a pump wave in a wide altitude content (up to about 600 km) in all X-mode HF heating experiments not depending on the excitation of HF-induced Langmuir and ion-acoustic plasma waves.…”

Numerical simulation of oblique ionospheric heating by powerful radio waves

“…Wuhan (30.4 • N, 114.0 • E), which is typical mid-latitude, is selected as the location of the heating transmitter. The magnetic dip of Wuhan is 45 • , which is nearly identical to that of Arecibo (Carlson et al, 2016). Figure 1 shows the initial ionospheric electron density and temperature profile at 00:00 LT adopted from the international reference ionosphere model (IRI-2012) (Bilitza et al, 2011).…”

“…The scientific concerns of ionospheric heating include a large range of plasma physics topics involving Ohmic/Joule heating, parametric instability, particle acceleration, Langmuir turbulence, VLF/ELF/ULF wave generation, etc. (Foster et al, 1983;Wong et al, 1971;Ungstrup et al, 1979;DuBois et al, 1990;Brinca et al, 1981).…”

Past, Present and Future of Active Radio Frequency Experiments in Space

“…Today there are four active HF facilities around the world. They are: SURA in Russia [Belikovich et al, 2007], EISCAT heating facility (built and formerly operated by Germany's Max-Planck Institute) in Norway [Rietveld et al, 2016], HAARP in Alaska, USA [Pedersen and Carlson, 2001], and most recently a new HF facility for the Arecibo 300 m antenna [Carlson et al, 2017]. Only Arecibo and the EISCAT HF facilities are co-located with incoherent scatter radars (ISRs), although HAARP has a small UHF phased array radar called the Modular UHF Ionospheric Radar (MUIR) which can receive HF-enhanced echoes normally seen with ISRs.…”