Galactic Cosmic Ray EEE

Transcription

1 Galactic Cosmic Ray EEE

2 First observations (FD) First rigorous experimental observation of Cosmic Ray Flux Decrease was obtained by S. E. Forbush in , after deep statisitcal analysis of data from precision cosmic ray meter, Cheltenham, Maryland and after studies on barometric and temperature effects.

3 Developments in FD search Pioneer 8 - interstellar medium effects? - Neutron Monitors

4 Energetic events on Sun Corona Photosphere: is what we see. A blackbody at 6000 K (below the ionization energy of H) oc Below the photosphere the temperature increases above the ionization energy of H. Plasma is opaque to light. From Chromosphere to Corona: The temperature increases up to tenth of million degrees. Why?

5 Magnetic confinement and plasmas Lorentz Force and precession A charged particle motion in magnetic field is confined within a spiral because of Lorentz Force F = qv x B A charged particle in motion induces a magnetic field modifying the external magnetic lines and enhancing the plasma confinement

6 Magnetic confinement and plasmas The heating from underlying sun layers provides a thermal pressure PT, tending to magnetic configuration disruption The kinetic energy injected by particle motion enhances the plasma confinement and the magnetic pressure PM Thermal pressure > Magnetic pressure Magnetic confinement in sun corona PT < PM: plasma is confined Heating from underlying sun layers Magnetic confinement enhancement due to plasma motion when PT becames greater than PM the field line is disrupted and the stored energy is release.then magnetic field lines reconnect

7 Energetic events on Sun Corona Flares Sudden increase in brightness Occurring in Sun Corona a belt confined along sun equator by magnetic fields Lasting secs to hour Etot 1025 J (Sun power P W) Observable in visible x-ray Gamma-ray

8 Energetic events on Sun Corona Coronal Mass Ejections Ejection of particles from Sun Corona (protons, electrons) Particles are accelerated from 20 to 2000 km/s Average 400 km/s Accelerated by the heating of underlying sun layers, confined by magnetic field Etot J (Sun power P W) Rate of occurrence: 0.25 day-1 (solar minimum) 4 day-1 (solar maximum)

9 Flare CME connection Flares are believed to be the results of re-heating due to manetic lined reconnection after a CME. However Flares and CME are not always associated, even if this happens in case of the strongest events.

10 Effects on the interplanetary medium Shock wave driven by ejected particles Particles ejected Accelerated particles by shock wave

11 Effects on Galactic Cosmic Rays Initial particle increase may happen (only for strong CME, due to shock acceleration)

12 GCRD VIAR-02 Flare class X :53:00 17:26:00 17:34:00

13 Data Download DQM page: Follow the daily DQM link...define the day download.csv trending

14 .xlsm import and preparation Two sets of data to be chosen Barometric correction set close to the event date with pressure fluctuations > 20 mbar within a good period for the telescope under analysis Forbush set Complete period Flux drop and recovery + some preceeding and following days.xlsm conversion via Import function and giving comma as a separator. Pile up data from different days in time order Daily DQM report contains redundant data erase superimposing periods

15 First sight to data Forbush datasheet Barometric correction datasheet Flux data Date conversion Pressure data

16 Uncorrected Trending (1 min) Several fluctuations visible

17 Pressure Rate anticorrelation Clear anti-correlation is visible Correction plot datasheet Plot data are from

18 Pressure effects on muon flux During the first phase the particle shower increase in particle number density because of interaction with air nuclei While the mean energy degrades, particles start to decay and being absorbed, thus decreasing the particle number density Pressure is a measure of the mass crossed during the flight: 1 bar = Pa = Nm-2 [P/g]=[M/S] 1 bar/g 1 Kgcm-2

19 Pressure effects on muon flux Relative particle flux variation is proportional to the depth travelled, thus to the pressure. di = μ dp I I =I 0 e μ(p P ) 0 The same initial flux, if P>P0, is measured to be lower at ground with respect to the days when pressure is lower. For tiny pressure variation: I =I 0 (1 μ (P P 0))=I 0 μ I 0 (P P 0)

20 Pressure effects on muon flux In order to identify particle flux variations due to Forbush effects the measured flux has to be corrected and referred to the same reference pressure P0 I 0=I +μ I 0 ( P P 0) I 0 I = μ (P P 0) I0 Absolute flux correction, linear approx Relative flux correction The absolute correction coefficient is therefore the slope of the regression line Rate vs Pressure While The relative correction coefficient is the same normalized to the Rate at reference pressure I0

21 Extracting the barometric coefficient Add a line trend or use LINEST function

22 Correcting data Corrected Trend Reference Pressure

23 Correcting data Rate-Pressure Anti-correlation Correction factor (Hz/mbar)

24 Averaging data Averaging data over 1-2 hours is effective in order to decrease the uncertainties on rate measurement, its statistical fluctuations The error on the mean value of a measurement is lower than the errors on single measurements by a factor N, where N is the number of measurements (consequence of Central Limit Theorem) thus σx σ x = N thus we average data over 1 hours and (other than FD) physical fluctuation become observable...

25 1 H averaged and corrected data N minutes average For averaging we use OFFSET function

26 Relative flux variation In order to perform comparison studies with other detectors we need to convert the absolute flux into relative flux After the definition of the reference flux Iref as the average on the first hours before FD event I hours I ref = hours=1... N N we derive the relative flux variation as follows: I rel hours I hours I ref = I ref

27 Relative flux variation N hours as reference Flux reference as the average on the first N hours Relative flux and errors

28 OULU Neutron Monitor Neutron Monitor in Finland, active since 1964, open data

29 OULU Neutron Monitor Fully customizable query

30 OULU imported data OULU Date is given as YYYY/MM/DD hh:mm:ss or fractional number of days Thus conversion is required Time bins are as requested by the query

31 OULU relative flux data OULU data also converted into relative count in order to allow comparison

32 VIAR-02 vs OULU GCRD

33 Extended task proposals: OULU-EEE correlation? Residuals? These tasks require good (<1h) time alignement between EEE and OULU time bins

34 Extended task proposals: Temperature effects - room temperature telescope fluctuations - outer temperature effects on air shower