Solar Radio Astronomy CHRISTOPHE MARQU BASIC SIDC SEMINARS source: - - PowerPoint PPT Presentation

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Solar Radio Astronomy CHRISTOPHE MARQU BASIC SIDC SEMINARS source: - - PowerPoint PPT Presentation

Mar 13, 2023 30 likes •846 views

Solar Radio Astronomy CHRISTOPHE MARQU BASIC SIDC SEMINARS source: NASA History The beginning 1902 : First (failed) attempt to observe radio waves from the Sun by Charles Nordmann (1902) in the French Alps, near Chamonix 1933:

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Solar Radio Astronomy

CHRISTOPHE MARQUÉ BASIC SIDC SEMINARS

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SLIDE 2

source: NASA

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History

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The beginning

  • 1902 : First (failed) attempt to observe radio

waves from the Sun by Charles Nordmann (1902) in the French Alps, near Chamonix

  • 1933: Discovery of cosmic radio emission by

Karl Jansky

  • 1944: First mention of solar radio emissions by
  • G. Reber (ApJ 1944) & first mention of

interferences!

  • 1946: First report of radar jamming by the Sun

(Hey, Nature)

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The beginning

  • 1902 : First (failed) attempt to observe radio

waves from the Sun by Charles Nordmann (1902) in the French Alps, near Chamonix

  • 1933: Discovery of cosmic radio emission by

Karl Jansky

  • 1944: First mention of solar radio emissions by
  • G. Reber (ApJ 1944) & first mention of

interferences!

  • 1946: First report of radar jamming by the Sun

(Hey, Nature)

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Grote Reber

source: NRAO

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SLIDE 7
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SLIDE 8
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The radio sun

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Solar imaging

❖Essentially interferometric imaging for having enough resolution ❖Sampling of the Fourier transform of the source ❖Imaging possible between ~ 60 MHz and a few 100s of GHz ❖Difficulties:

  • Large source
  • High temporal and intensity variability
  • Ionosphere at low frequency

Thompson et al.

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Solar imaging

❖Essentially interferometric imaging for having enough resolution ❖Sampling of the Fourier transform of the source ❖Imaging possible between ~ 60 MHz and a few 100s of GHz ❖Difficulties:

  • Large source
  • High temporal and intensity variability
  • Ionosphere at low frequency

Thompson et al.

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Solar imaging

❖Essentially interferometric imaging for having enough resolution ❖Sampling of the Fourier transform of the source ❖Imaging possible between ~ 60 MHz and a few 100s of GHz ❖Difficulties:

  • Large source
  • High temporal and intensity variability
  • Ionosphere at low frequency

Thompson et al.

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Solar imaging

❖Essentially interferometric imaging for having enough resolution ❖Sampling of the Fourier transform of the source ❖Imaging possible between ~ 60 MHz and a few 100s of GHz ❖Difficulties:

  • Large source
  • High temporal and intensity variability
  • Ionosphere at low frequency

Thompson et al.

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Nançay 150 – 450 MHz

151 MHz 445 MHz

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VLA 50 MHz – 50 GHz (non solar dedicated)

NRAO & S. White NRAO 4.6 GHz

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Nobeyama 17 & 34 GHz

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LOFAR 20 – 240 MHz (non solar dedicated)

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LOFAR 20 – 240 MHz (non solar dedicated)

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LOFAR 20 – 240 MHz (non solar dedicated)

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Dynamic spectra

  • Solar emission outside flaring events evolve

slowly (timescale of days)

  • Energy release can occur on timescales of

milliseconds

  • Accelerated electrons emits radio waves

through different mechanisms

  • Spectral signatures give access to the flaring

scenario

Source: P. Lantos type III

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Group of type III/type U bursts

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Type IIIs, type II and type IV linked to M flare

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Type II, high freq. counterpart with M flare

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Variabilility of the quiet solar emission

  • Continuum emission: no lines
  • Thermal emission (hot coronal gas)
  • Gyro emission (in AR)
  • Slow variation from day to day
  • Measurements since WWII in several

bands (1000 – 4000 MHz)

“The excitement of the eclipse observations [at 10.7 cm] was soon followed by the sobering thoughts that solar radio emission from sunspots would be variable…”

  • A. Covington, Proc. NRAO Workshop, 1983
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Solar Flux radio Observatories

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Solar Flux radio Observatories

2800 MHz 1000 MHz 2000 MHz 3750 MHz 9400 MHz 17000 MHz 245 MHz 410 MHz 610 MHz 1415 MHz 2695 MHz 4995 MHz 8800 MHz 15400 MHz

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SLIDE 27
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Antenna & telescopes

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Gain and radiation patterns

SPADE gain pattern; A. Martinez

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Dipole antenna

  • Detection of the Electric component of the

E.M Wave

  • Half-wave dipole : tuned to a given frequency
  • Resonant element

source: wikipedia source: Schwarzbeck

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Dipole antenna

  • Detection of the Electric component of the

E.M Wave

  • Half-wave dipole : tuned to a given frequency
  • Resonant element

source: wikipedia source: Schwarzbeck

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Antenna derived from dipoles

YAGI SIMULATED RADIATION PATTERN

  • One “active”

element

  • Passive

elements drive waves interfering additively forward and destructively backward

  • Tuned for one

frequency

source: A. Martinez source: BRAMS - BISA

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Antenna derived from dipoles

YAGI SIMULATED RADIATION PATTERN

director reflector radiator

  • One “active”

element

  • Passive

elements drive waves interfering additively forward and destructively backward

  • Tuned for one

frequency

source: A. Martinez source: BRAMS - BISA

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SLIDE 34

Antenna derived from dipoles

YAGI SIMULATED RADIATION PATTERN

director reflector radiator improved gain

  • One “active”

element

  • Passive

elements drive waves interfering additively forward and destructively backward

  • Tuned for one

frequency

source: A. Martinez source: BRAMS - BISA

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Antenna derived from dipoles

LOG PERIODIC ANTENNA

  • All elements “actives”
  • successive elements

connected out-of-phase

  • Constructive

interferences forward

  • “Flat” gain &

broadband

source: A. Martinez

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Antenna derived from dipoles

LOG PERIODIC ANTENNA

  • All elements “actives”
  • successive elements

connected out-of-phase

  • Constructive

interferences forward

  • “Flat” gain &

broadband

source: A. Martinez

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Antenna derived from dipoles

LOG PERIODIC ANTENNA

  • All elements “actives”
  • successive elements

connected out-of-phase

  • Constructive

interferences forward

  • “Flat” gain &

broadband

source: A. Martinez

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Fat dipoles

  • Broadband (here 10 – 80 MHz)
  • Mismatch in electrical properties is

compensated by an active element (active balun with amplifier)

source: LWA – NENUFAR for SPADE source: LWA – NENUFAR / LONAMOS

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Horn antenna

  • No resonant element (broadband)
  • Provide a “soft” transition between free-space

electrical conditions to the ones of wave guide and electronics

  • Radiation characteristics can be easily

(analytically) calculated

  • High gain and lower side lobes
  • Used as feed systems and absolute calibration

system

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Horn antenna

  • No resonant element (broadband)
  • Provide a “soft” transition between free-space

electrical conditions to the ones of wave guide and electronics

  • Radiation characteristics can be easily

(analytically) calculated

  • High gain and lower side lobes
  • Used as feed systems and absolute calibration

system

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Horn antenna

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Horn antenna

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Solar radio telescopes

LEARMONTH, source: Kennewell, 2008

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Solar radio telescopes

LEARMONTH, source: Kennewell, 2008 source: Nobeyama observatory

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Solar radio telescopes

Analytical calculation of ANT34 radiation field

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Receiving systems

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What do we measure?

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Flux density

ΔΩ ΔΩsun

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Flux density

ΔΩ ΔΩsun

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Flux density

ΔΩ ΔΩsun

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Different external noise contributions

Antenna temperature Sun dominates, but here beam size=solar diameter

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System noise

Freq [MHz] T_Rx [K] 611 360 1060 470 1415 1090 Best is to put first in the chain element with hi gain and low noise 1: cable 3: cable 4: receiver 2: LNA

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Example

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Receivers

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Spectrographs

Wide band solar emissions High dynamic range Fast temporal evolution Multi channel receivers Sweep frequency instruments Wide band FFT spectrometer

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Multichannel

Dumas et al, 1982

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Sweep frequency

  • Made from consumer electronics

hardware PC-controlled hardware with RS232 connection

  • Software for automatic observations

(frequency program, schedule…)

  • Programmable frequencies

Parameter Specification Frequency range 45-870 MHz Frequency resolution 62.5 kHz Bandwidth 300 kHz (-3dB) Dynamic range ~50 dB Sensitivity 25±1 mV/dB Noise figure <10dB Sampling rate 800-1000 samp/s Weight 800g Dimensions 11x8x20.5 cm http://www.e-callisto.org CALLISTO

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Multi band FFT spectrographs

Korean Solar Radio Burst Locator, Dou et al. 2009 0,5 -18 GHz

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Multi band FFT spectrographs

Korean Solar Radio Burst Locator, Dou et al. 2009 0,5 -18 GHz

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Multi band FFT spectrographs

Korean Solar Radio Burst Locator, Dou et al. 2009 0,5 -18 GHz

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CESRA SUMMER SCHOOL 2015

“Cheap” digital spectrographs

41

In the spirit of the Callisto instrument “cheap” digital receivers can be turned into solar spectrographs Software Define Radio Gnuradio Python, C Sweep/FFT spectrometer Steps of 25 MHz BW Fully programmable Open source

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Humain

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The Humain station

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The Humain station

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The Humain station

Weather station (RMI) Meteor & whistler radio antenna (BISA) Stellar optical telescopes (ROB) Solar radio spectrographs (ROB)

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Humain: Solar instruments

6-m dish Automated operations, Sun tracking ~7h30 – 16h00 UT VHF antenna (piggy back) UHF antenna at focus

  • VHF antenna (45 – 450 MHz)
  • Callisto receiver
  • ARCAS receiver
  • UHF antenna (275 – 1495 MHz)
  • HSRS receiver
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Humain: Solar instruments

Callisto ARCAS HSRS Type Analog receiver Digital Digital Frequency band 45 – 447 MHz 45 – 450 MHz 275 – 1495 MHz Frequency resolution 63 kHz 98 kHz 98 kHz Time resolution 250 ms ~ 84 ms ~ 250 ms # of frequencies 200 ~ 4.2 k ~ 12.5 k

Data available in near realtime http://sidc.be/humain

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New project: code name ANT34

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New project: code name ANT34

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New project: code name ANT34

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New project: code name ANT34

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New project: code name ANT34

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SPADE

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Interferences and spectrum management

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CESRA SUMMER SCHOOL 2015

Interferences

  • Radio spectrum usage is regulated at national & international levels
  • Radio astronomy is protected by ITU (recommendation ITU-R RA. 769)
  • Protected and shared bands for RA

49

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Interferences

3MHz 30 MHz 300 MHz 3 GHz 30 GHz

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Interferences

3MHz 30 MHz 300 MHz 3 GHz 30 GHz

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RFI level from the e-Callisto network

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Zebra burst during type IV Bouratzis et al. 2014

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Zebra burst during type IV Bouratzis et al. 2014

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Zebra burst during type IV Bouratzis et al. 2014 Electronics of LED lamp Lawn cutter Monstein, 2013