Help with circle and arrows diagram with PGFPLOTS

Question

I'm trying to make a plot similar to this one but I'm having a really hard time. If anyone can help me getting the details, I'll appreciate.

I thought I couldn't post questions like this, but as I've seen some questions like those asking for plots similar to xkcd's, I believe it might be OK.

My far-from-good example is here. My circle has a radius=sqrt(2), but it really doesn't matter.

\documentclass{article}

\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\begin{document}

\begin{tikzpicture}

\begin{axis}[
height=20cm,
width=20cm,
xmin=-2.5, xmax=2.5,
ymin=-2.5, ymax=2.5,
only marks,
axis x line=none,
axis y line=none
]

\draw (axis cs:0,0) circle[radius=1.41421356237];

% circle
\addplot [mark=*, mark size=0.3cm,color=red]
coordinates {
(-1,-1)
(1,1)
};
\addplot [mark=*, mark size=0.3cm,color=red]
coordinates {
(-1,1)
(1,-1)
};
% black arrows
\addplot [mark=none,color=black,
quiver={u={x}, v={-x},scale arrows=0.4}, ->]
coordinates {
(-1,-1)
(1,1)
};
\addplot [mark=none,color=black,
quiver={u={-x}, v={-x},scale arrows=0.4}, ->]
coordinates {
(-1,1)
(1,-1)
};
% blue arrows
\addplot [mark=none,color=blue,
quiver={u={x}, v={-x-0.5},scale arrows=0.5}, ->]
coordinates {
(-1,-1)
(1,1)
};
\addplot [mark=none,color=blue,
quiver={u={-x}, v={-x-0.5},scale arrows=0.5}, ->]
coordinates {
(-1,1)
(1,-1)
};

\addplot [mark=*, mark size=0.3cm,color=blue] coordinates {
(1.41421356237,0)
(-1.41421356237,0)
(0,1.41421356237)
(0,-1.41421356237)
(1.41421356237,0)
};

\end{axis}  
\end{tikzpicture}
\end{document}

which gives me this:

Answer 1

Instead of pgfplots construction, you can use an alternating style which are slightly verbose here (repetition of ->, ultra thin etc.) Luckily the structure is easy to identify. You can furnish further according to your needs.

EDIT: Thanks to JLDiaz' color-seeing eyes, I took a stab on the green arrows. Hope it hits the right one :)

\documentclass[tikz]{standalone}
\usetikzlibrary{calc}

\begin{document}

\begin{tikzpicture}[>=latex,
cnode/.style={circle,inner sep=3pt,outer sep=0},
myline/.style={ultra thin,->}
]
\def\myarrowlen{5mm}
\pgfmathsetmacro{\myradius}{sqrt(2)}

\node[draw,circle,minimum size=2*\myradius cm] (bigc) at (0,0) {\tiny +};

\foreach \x in {1,...,8}{
\ifodd\x\relax
    \node[cnode,fill=red] (n-\x) at (bigc.45*\x) {};
    \draw[red,myline] (n-\x)  -- ($(n-\x)!-\myarrowlen!(bigc.45*\x+45)$);
    \draw[red,myline] (n-\x)  -- ($(n-\x)! \myarrowlen!(bigc.45*\x+45)$);
\else
    \node[cnode,fill=blue] (n-\x) at (45*\x:\myradius) {};
    \draw[blue , myline] (n-\x) -- ($(n-\x)!-\myarrowlen!(bigc.45*\x+45)$);
    \draw[green, myline] (n-\x) -- ($(n-\x)! \myarrowlen!(bigc.45*\x-45)$);
    \draw[     , myline] (n-\x) -- ++({45*(\x-2)}:\myarrowlen);
\fi
}
\end{tikzpicture}
\end{document}

Answer 2

Here is an alternative solution using metapost (I used ConTeXt, but you can use standalone metapost, or metapost embedded in LaTeX as well).

The main difference from percusse's solution is that instead of specifying the length and angle of the arrows, I calculate it based on the location of the nodes. Unlike TikZ, metapost does not provide a nice way to shorten paths, so I define a macro that does that.

\startMPinclusions
  vardef shorten(expr p, q, d) =
    % p = start point
    % q = end point
    % d  = distance
    newpair qq;
    qq := q - d*dir(angle(q-p));
    (p -- qq)
  enddef;
\stopMPinclusions
\starttext
\startMPpage[offset=3mm]
  newnumeric u; u := 2cm; % Radius of the circle
  newnumeric w; w := 3mm; % Radius of nodes
  newnumeric d; d := 0.25mm; % Distance between arrows

  draw fullcircle scaled (2*u);

  newpath node;
  node := fullcircle scaled w;

  % Use 10 points to avoid modular arithematic
  for i = 0 upto 10 : 
      z[i] = u*dir(45*i);
  endfor

  newpair mid_point ;
  newpair scratch_point ;
  newnumeric tangent_angle;

  for i = 1 upto 8 :
    if i mod 2 = 0 : % blue node
      % Caclulate coordinates
      mid_point := 0.5[z[i], z[i-1]];
      scratch_point := 2*z[i] - 0.5(z[i] + z[i+1]);

      % Draw arrows
      drawarrow shorten(z[i], mid_point, d) withcolor green;
      drawarrow shorten(z[i], scratch_point, d) withcolor blue;

      tangent_angle := angle(0.5[mid_point, scratch_point] - z[i]);
      scratch_point := z[i] + abs(z[i] - mid_point)*dir(tangent_angle);

      drawarrow shorten(z[i], scratch_point, d) withcolor black;

      % Draw node
      fill node shifted z[i] withcolor blue;
    else : % red node
      % Caclulate coordinates
      mid_point := 0.5[z[i], z[i+1]];
      scratch_point := 2*z[i] - mid_point ;

      % Draw arrows
      drawarrow shorten(z[i], mid_point, d) withcolor red;
      drawarrow shorten(z[i], scratch_point, d) withcolor red;

      % Draw node
      fill node shifted z[i] withcolor red;
    fi
  endfor

\stopMPpage
\stoptext