%0 Journal Article %T Dispersion measure variations observed in the direction of the millisecond pulsar PSR B1821-24. %+ Laboratoire de physique et chimie de l'environnement (LPCE) %+ Observatoire de Paris - Site de Meudon (OBSPM) %+ Unité Scientifique de la Station de Nançay (USN) %A Cognard, Ismaël %A Lestrade, Jean-Francois %< avec comité de lecture %@ 0004-6361 %J Astronomy and Astrophysics - A&A %I EDP Sciences %V 323 %N 1 %P 211-216 %8 1997 %D 1997 %Z 1997A&A...323..211C %K PULSARS: GENERAL %K PULSARS: INDIVIDUAL: PSR B1821-24 %K ISM: GENERAL %K STARS: KINEMATICS %Z Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR]Journal articles %X High-precision timing observations of the millisecond pulsar PSR B1821-24 have been conducted at the Nancay radiotelescope between 1.37GHz and 1.7GHz since January 22, 1992 until January 10, 1996. This dense and precise multi-frequency timing series has allowed secular variations of the dispersion measure as high as 0.005pc/cm^3^/year in the direction of this pulsar to be determined. The index β of the power-law spatial spectrum of the electron density fluctuations has been determined for the first time in the direction of this pulsar and is 3.727+/-0.211, a result consistent with a Kolmogorov turbulent medium. The diffractive time scale τ_d_ is also determined to be 50+/-_ 40_^183^ s and is relatively consistent with the determination based on the space velocity of PSR B1821-24. We also provide a new proper motion for this pulsar for which the declination component is for the first time inconsistent with zero. %G English %2 https://insu.hal.science/insu-02612447/document %2 https://insu.hal.science/insu-02612447/file/1997A%2BA___323__211C.pdf %L insu-02612447 %U https://insu.hal.science/insu-02612447 %~ OBSPM %~ INSU %~ CNRS %~ UNIV-ORLEANS %~ USN %~ LORIA2 %~ OSUC %~ LPC2E %~ PSL %~ OBSPM-PSL %~ TEST3-HALCNRS