Diffraction scintillation at 1.4 and 4.85GHz

V.M.Malofeev, O.I.Malov, S.A.Tyul’bashev

PRAO, Russia

W.Sieber

Hochschule Nederrhein, Germany

A.Jessner, R.Wielebinski

MPIfR, Germany

Introduction• Most important characteristic of the turbulent

interstellar medium is the three-dimensional spatial spectrum of the electron density fluctuations: a Gaussian or power law.

• The aim of our project was to obtain the form of turbulence spectrum for different regions of the sky and for pulsars which are at different distances.

Observations• 100m RT in Effelsberg during 2-12th Sept. 2003

• 15 pulsars at 1.4GHz and 6 at 4.85GHz

• Criteria: strong objects with good SNR, pulsars should clearly show scintillation

• to obtain dynamic spectra the total receiver bandwidht must be much broader then the decorrelation bandwidth of pulsars

• 1.4GHz: 30chan x 1.33MHz= 40MHz

• 4.85GHz: 8chan x 60MHz=480MHz

• two polarization; flux measurements every 30sec; duration of observations 1-10hours

PSR 0329+54 (1.41GHz)• Example of dynamic spectra in the strong

scintillation regime

PSR 1929+10 (1.4GHz; 7 Sept.)• Example of dynamic spectra in the weak(?) scin.regime

PSR 1929+10 (1.4GHz)• Scin. data; • ACF time function; • CCF frequency

function; • power spectrum;• structure function

PSR 2020+28 (1.4GHz)• 03 Sept. - strong scint; 10 Sept. - lensing effect

PSR 2020+28 (1.4GHz)• Scint. data;

• ACF time function;

• CCF frequency function;

• power spectrum

• structure function

PSR 1642-03 (4.85GHz)• Dynamic spectra in the weak scin. regime

PSR 0355+54 (4.85GHz)• Dynamic spectra in the strong(?) scin.regime

PSR 0355+54• Scint. data;• ACF time function• CCF frequency

function• Power spectrum• Structure function

Number of pulsars

Freq Dec.time Dec.band. Spectrum Str.funct.

1.4GHz 11 8 11(2.7+-0.4) 11(1.5+-0.3)4.85GHz 5 1 5(2.8+-0.4) 5(1.2+-0.4)

Conclusion• We have obtained scintillation data for 11 PSR at

1.4GHz and 5 PSR at 4.85GHz: the decorrelation time and bandwidth, power low index for spectra and structure function

• Possible lensing effect (focal spot effect) have been detected for a few pulsars near the critical frequency