Emmision%20of%20the%20remarkable%20pulsar%20B0943 10:%20Continual%20changes%20in%20the%20subpulse%20drift%20rate%20and%20in%20integrated%20pulse%20shape,%20intensity%20and%20polarization%20at%20frequencies%20of%20327,%20112,%2062%20and%2042%20MHz.%20%20Svetlana%20A.%20Suleymanova%20(PRAO%20,%20Pushchino)%20Joanna%20M.%20Rankin

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Emmision of the remarkable pulsar B094310
Continual changes in the subpulse drift rate and
in integrated pulse shape, intensity and
polarization at frequencies of 327, 112, 62 and
42 MHz. Svetlana A. Suleymanova (PRAO ,
Pushchino)Joanna M. Rankin (University of
Vermont, Vermont)

• We present data of new observations carried out
  at the Pushchino Radio Astronomy Observatory
  (PRAO) at low radio frequencies 42, 62 and 112
  MHz of a well known mode switcher B094310.
  Earlier observations at 327 MHz (Arecibo) have
  shown remarkably continual changes in subpulse
  drift rate and in the integrated-profile shape
  with duration of several hours in its Burst
  mode. Observations at PRAO have shown that the
  changes in the pulse shape during B-mode
  life-time are strongly frequency dependent,
  namely the changes in components amplitude ratio
  are more dramatic at 327 112 MHz as compared
  with those at 62 42 MHz.

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The component's peak intensity ratio- A(2/1)
histograms in B-mode of the pulsar B094310 at
near 42, 62, 112 MHz (PRAO, 2005-2008) and 327
MHz (Arecibo, 2003). It is obvious that
components amplitude ratio A(2/1) changes in the
wider range at higher frequencies.
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Integrated-pulse profile evolution during the
Burst mode lifetime for pulsar B094310. The
profile component-amplitude ratio A(2/1) as a
function of the circulation time of the
20-subbeam "carousel" at 327 MHz (stars), 112 MHz
(crosses), 62 MHz (open circles) and 42 MHz
(diamonds). Each averaged profile is comprised of
256 individual pulses (IP) at 327 MHz, 190 IP at
112 MHz, and 860 IP at 42 62 MHz. The vertical
dashed line indicates the B-mode onset time.
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Amplitude-fluctuation spectra of the individual
pulse sequence following the B-mode onset at
pulse 101 detected in the observations at PRAO
02 December 2007 at 62 MHz. The spectrum of the
whole sequence has three maxima (left panel)
resulting from three groups of pulses drifting
with different rates (right panel). This example
show that the subpulse-drift rate changes very
rapidly over the first 15 minutes after B-mode
onset.
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Systematic changes in B094310's average profile
form as a function of time at the frequencies
112 MHz (crosses), 62 MHz (open circles) and 42
MHz (diamonds). The turbulent stage of the
pulse shape evolution lasts nearly 40 minutes
after the B-mode onset. The vertical dashed line
indicates the B-mode onset time.
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The linear polarization percentage at the peak of
the first component as a function of amplitude
ratio A(2/1) of the two component peaks at 327
MHz (crosses) and 62 MHz (circles). The data fit
to exponential functions which are marked by
dashed line (62 MHz) and solid line (327 MHz).
The X-axis is given in descending order with
A(2/1)1.34 at B-mode onset and A(2/1)0.12 at
B-mode offset.
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Systematic increasing of the linear polarization
percentage at the peak of the first component as
a function of time at 327 MHz. The linear
percentage was calculated as a ratio of the
linearto-total power amplitudes at the longitude
of the main (first) component of the average
profile. Each average is comprises of 512
individual pulses, or 9.4 min. The average
profile linear polarization varies markedly
within the range between 3 and 50 during 4
hours between onset and offset of B-mode. Since
P3 has been measured from intensity-fluctuation
spectra for each individual pulse sequence, the
corresponding time has been derived from the
CT-Time dependence.
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Histograms of the CT data based on Arecibo-2003
observations (dark columns) at 327 MHz and
PRAO-2005-2008 observations (open columns) at 112
MHz. The turnover of the tendency at CT between
37.75 and 38 is caused increased probability of
B-offsets here. The arrows mark the CTs at the
time preceding the B-mode offset (1h 20m, 1992,
430 MHz, Arecibo and 3h 50m, 2006, 112 MHz, PRAO).
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Summary

• 1. Recent observations at PRAO (2005-2007) at
  the low frequencies of 112, 62 and 42 MHz have
  shown that the changes in the pulse shape during
  B-mode life-time are strongly frequency
  dependent, namely
• The changes in the component-amplitude ratio
  are less at 62 and 42 MHz as compared with those
  at 327 and 112 MHz .
• The (A2/A1)-CT relation at lowest frequency of
  42 MHz can be approximated by two linear
  functions implying different behaviors of A2/A1
  above and below some critical CT.
• Question Can refraction cause this frequency
  dependence?
• 2. The duration of each individual event of the
  B-mode may vary significantly.
• T 1h20m, 1992, 430 MHz, Arecibo T 3h50m,
  2006,112 MHz, PRAO
• Question What is the critical condition in
  pulsar magnetosphere that cause the
• offset of the B-mode at so different age ?

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• 3. The pulsar exhibits the utmost difference in
  the pulse shape at frequency range 327-42 MHz
  during 30 minutes after B-mode onset.
• Question What is happening in the pulsar
  magnetosphere during these 40 minutes?f
• 4. A measurements at 62 and 327 MHz have shown
  that the linear polarization of the stronger
  (first) component of the integrated profile
  continually increases during B-mode lifetime.
• Question We have reasons to suggest that the
  increasing of linear polarization percentage is
  connected with redistribution of the energy
  between polarization modes in favor of PPM which
  is mostly characteristic of the strong
  intensities. Can we then to propose that the
  pulsar B094310 in its B-mode continually flares
  up? Is it B-mode or F-mode?

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Interpretation

• The frequency dependence of the phenomenon
  suggests that propagation effects in the
  magnetospheric plasma play a marked role. Petrova
  (2002) has shown that refraction can cause a
  significant redistribution of the intensity in
  the emission beam. As the refraction is
  determined mainly by the plasma-density gradient
  within the polar flux tube, the continuous B-mode
  pulse-shape changes may imply a correspondingly
  slow redistribution of the plasma outflow. The
  refraction is expected to be more intense at
  higher frequencies (Lyubarskii Petrova
  1998)i.e.,gt 1 GHzwhere rays are emitted nearly
  parallel to the local magnetic field. To explain
  B094310s observed pulse changes at low
  frequencies (327-40 MHz) by refraction, some
  exotic magnetic field geometry is needed like the
  twisted up one suggested by initially Rankin,
  Suleymanova Deshpande (2003).